"I want to go to places like France and Germany for the summer vacation."
You can take a laundry list of verbs, conjugate them in plain past form (～った) and add a り, and it just means "among doing this, and this, and this..." Kind of like using や and などwith nouns (which Duolingo does not have a lesson on.)
If you take a bunch of verbs and string them together with their ~て forms, it implies either a time passing ("I did this and then this.") or a causation (like "because.") When you use ~たり, it's just a bunch of stuff in no particular order.
The meaning stays the same, of course, but I suppose Duolingo wants to make sure you know which is which, so you don't accidentally think フランス is Germany, for example.
And what exactly might be wrong with 夏休み (rejected as incorrect in an answer otherwise exactly as above)?
The ending of the verbs implies there are a lot of things going on. Take any verb, put it in ～た form. This is "plain past tense." (Okay, so here is the first problem if you are using ONLY Duolingo to learn. They do not as yet have a lesson on "plain past tense." In a nutshell, it is the same as ～て-form (Just like when you change a verb to give a command or say "please."), except that instead of ～て we are going to use ～た. The good news is that Japanese is very logical and there are only two irregular verbs in the whole language （する・くる） and even they act normally once you get past their initial weirdness.) So once you get ～た form down, all the verbs will act the same.
Then you just add り so you get～たり. This particular verb ending implies a list of stuff you are doing.
I'll give you some help with ～た form. Remember, it also works for ～て form. Step 1: You have to know the dictionary form (AKA plain form, AKA じしょかたち) for the verb in question. If the verb ends with つ or う or is a five-step る-verb, take off the つ or る , and it's going to become った。 (examples: たつー＞たった・ うたうー＞うたった・ のぼるー＞のぼった） If the verb ends with く, the new ending will be いた。 （example: かくー＞かいた） If the verb ends with す, it will become した。 （はなすー＞はなした） If the verb ends in ぶ, む, or ぬ, it will change to んだ。 （あそぶー＞あそんだ・ よむー＞よんだ・ しぬー＞しんだ） If the verb is a one-step る-verb (hint: These generally have an えor い sound right before the る), just take it off and add た。 （たべるー＞たべた） The two irregular verbs: するー＞した くるー＞きた
Hope this helps! Remember that ～て form works the same way, so you get two for the price of one!
there are only two irregular verbs in the whole language （する・くる）
If the verb ends with く, the new ending will be いた。 （example: かくー＞かいた）
Given the specific sentence we're discussing and the verbs it contains, this seems to have been rather a big oversight... 行く (いく) having 行った (いった) as its past tense clearly goes against these two blunt assertions. XD
Thank you for chiming in, Testmoogle!
Yes, I suppose you could say "There are 2 1/2 irregular verbs in Japanese!"
Because Japan has historically been so literate, you can see some evolution of 「 いく」 in the written language. But you are right; this one is weird only in the ～て and ～た forms, where you will get a little っ instead of the expected き。（If you care about geeky stuff, the き gradually changed into an い and then turned into the little っ. ）
You don't provide enough words or phrases to allow for a correct translation.
I'm annoyed that you are leaving out words that are necessary to complete the repetitious sentences. Enough already!
It's impossible to answer this question correctly when you don't GIVE PEOPLE ALL THE WORDS THEY NEED TO ANSWER THE QUESTION.
For me it was impossible to answer it wrong because the whole answer was already filled in. ^^;
Maybe there is an alternative way to formulate an answer while not using some of the words as shown in the translation above. If you can tell what exactly were given then we may be able to help ^^.
There are lots of other ways to formulate this sentence as well; for example using the particles や and など (which I have not seen yet in the entire Duolingo Beta tree. Maybe now that they've added crowns?)