Translation:I need some good advice but people give me only unhelpful advice.
Actually, дают agrees with its plural subject люди. I believe the confusion comes from the fact that the English word "advice" is uncountable, and therefore has no plural form; replace it with, for example, apples, and you'll realize that the same thing happens in English: "I need a good apple but people only give tasteless apples."
In other words you're right, there is an implied советы.
Well, I'm no grammarian, but the literal translation of this sentence is: "I need a useful advice, but people give the useless ones only."
I know it's gramatically incorrect. I hope it will help to get the idea, though.
A more natural English translation would be "I need good advice but people don't give me any"
I need some useful advice but people only give me a useless one _ not accepted. WHY?
The word "advice" is an unusual word. It is defined as an "uncountable noun.".
In this sentence, even though the word is grammatically singular, its meaning implies plural. But your phrase "a useless one" is strictly singular and does not match the implied plural "advice." So, there is a lack of parallelism that sounds wrong to an English speaker. This is why DL's translation had to fix the problem by using the word advice twice even though the Russian only used it once.
This is a inappropriate sentence for DL to use at this level of Russian study.
Does а have to be translated as "but" here, could it also be "and"?
Can anyone kindly explain to me why my answer in incorrect? "I need a good advice, but people only give me useless ones"
Because "advice" is a mass noun and cannot take the singular indefinite article. "I need a good piece of advice..." would be fine
de nada Lots of words in English can only take the definite article or a phrase of quanitity eg "I want some sugar/the sugar" as opposed to "I want a sugar cube". Compare "How much sugar?" with "How many sugarcubes?"
However, you can say "sugar" but only in the chemical sense ie "glucose is a sugar"
"Water" is similar, but again you can say " a water" in the sense of "Do you want a water?" meaning "Do you want a bottle of water (as opposed to fruit juice)". the whole thing is very idiomatic
Мне нужен полезное упражнение, а люди дают только бесполезное. ))
Sorry, I don't really mean that, I just couldn't resist. But this exercise does have a problem - the difference in structure between Russian and English demands either a literal translation - which isn't accepted - or a free one we can't really predict. ((
Can I advance my usual solution: accept a literal translation, but suggest a better free one? Literally the best I could think of was "I need good advice, and people give only useless", which I think is still acceptable grammar, though elliptical.
П.С. FWIW, Yandex matches my translation almost exactly, whereas Google makes a grammatical mistake: "...useless ones".