"Él había decidido no salir más con ellos."
Translation:He had decided to not go out with them anymore.
I believe the 'no' always comes before the verb, so "no salir mas frequentemente", although it seems an odd phrase to actually use in Spanish. I guess most would say they are going to continue going out with the same frequency (salir con la misma frequencia que antes), or go out less often (salir menos frequentemente, or just salir menos).
So-called split infinitives are perfectly fine in general. In fact, a split infinitive is sometimes the only elegant way to express a particular thought. People who try to avoid split infinitives sometimes change the meaning of a sentence for no good reason.
The canard that there is something fundamentally wrong with split infinitives comes from people who insisted that English has to work precisely like Latin, where the phenomenon does not exist. But the best English authors have never agreed with the contention.
I'd like to understand why my translation is not accepted: "he had decided to not leave again with them." In fact, if I translated the English to Spanish, I would use the same Spanish we are asked to translate. "Salir" means "to leave" doesn't it? Any comment or explanation why my translation was wrong?
It's a subtle problem, but it should be easy to understand if you consider the task of translating Duolingo's 'official English translation back to Spanish:
"He had decided to not go out with them anymore."
In English, go out can mean all sorts of things. The basic meaning is leaving the house (or wherever you are at the moment). But it can also refer to spending the evening/night in a public place, to ending something (such as a game or the burning of a candle) or to ceasing to be due to loss of material.
In this English sentence, we cannot be completely sure which meaning is intended, but without further context almost everybody would read it in the sense of spending the night in a public place, because this is where we have all heard similar sentences. Example:
"He had decided to not go out with them anymore. Last time they had drunk way too much, and he had ended up in a jail cell with them."
Other interpretations are quite far-fetched and require somewhat strange contexts:
"He had decided to not go out with them anymore. Last time he had tried, they had knocked him unconscious while he was trying to bind his shoes. So today he was going to use the back door while they left through the front door."
"He had decided to not go out with them anymore. They just didn't understand the game, and in his experience with a good hand of cards such as the one he had right now, it made more sense to face the opposing party alone."
Now back to the Spanish sentence. In it, salir also has several possible meanings, but it appears that all of them can be captured with the English verb go out. Moreover, the most likely meaning of salir in this context (spending the night out) corresponds to the most likely meaning of go out. This close correspondence, which is not always possible, is why here go out is the best translation. The problem with your translation (as well as with go away) is that with it the most likely interpretation of the original sentence is no longer possible.
As the most likely interpretation, which you have lost, is so much more likely than the one you have chosen to translate, and an excellent translation is available that works for all interpretations, it makes sense to reject your translation even though given an appropriate unlikely context it would definitely be correct.
Note I am not saying your translation is wrong. It's just a bit too far on the wrong end of the correctness scale. On the other hand, if someone proposes it as a new correct solution, it might end up accepted.
That's a brave and lengthy answer. You seem to say that the verb "salir" has a special intention linked to it that a simple departure doesn't have. In other words, one doesn't just "leave" a house when he "sale," he leaves with someone or do something. I gather you would never use "salir" to translater the following English phrase, "he had decided to not leave again with them," into Spanish?
No, that's not what I wrote, or at least not what I meant. When you say in English, "I am going out today", then you can't replace this by "I am leaving today", even though in principle go out and leave are synonyms. This is because go out is used for spending the night out, and we know instinctively when it's almost certainly used in that sense rather than as a synonym for leaving. The same happens with salir in Spanish. Every Spanish speaker knows instinctively that the Spanish sentence is almost certainly about spending the night together in a pub or theatre or similar place, not about leaving the house (or country) as a group and then maybe going in different directions.
When we start with your English sentence ("He had decided to not leave again with them"), then we already know that it's not about going out to spend the night together. A straightforward translation is the Spanish sentence we started with: "Él había decidido no salir más con ellos". That's an acceptable translation because in most contexts where the English sentence even makes sense it would be interpreted as intended. (See my "knocked him unconscious" example for such a context.) It would be better to find a synonym of salir that excludes the partying sense. The only thing I have found in that direction is salirse, which according to my dictionary is only for straightforward leaving. I guess you could say: "Él había decidido no salirse más con ellos". In the absence of such synonyms, the translation with salir would be the only option that stays close to the original sentence structure.
Más is being used in an idiomatic sense here that overshadows the literal sense. I don't know if it's possible to express your sense with this sentence, but it's at least unusual. Normally one would choose a different formulation to be clear, such as this:
"Él había decidido no salir más frecuentemente con ellos."
Let's say this man goes out with them twice a week and has been asked if he'd go three or four times but has decided not to go out with them more than the twice. Wouldn't the sentence be written in the same way. Instead of más meaning anymore it just means more. Can anyone help with this?