"They have vacation in July and August."
Translation:Ils ont des vacances en juillet et août.
"vacation" (singular in English) = vacances (feminine plural in French). Hence you must use the plural indefinite article des.
As far as I know, "vacation" can be used in the plural form as well, for instance "I spent my vacations...". https://www.linguee.de/deutsch-englisch/search?source=auto=on+my+vacations But note that "to be on vacation" just exists in the singular form.
In French it has to be the plural "les vacances".
But one does not go on many "vacation" which is how it is used in the lesson.
"avoir des vacances" is an idiomatic expresssion. The plural indefinite article "des" is needed because the holidays are not specified.
This sentence doesn't seem quite correct in english. Maybe it is because in the UK we don't say "Vacation" but rather "Holiday" and would say "They have A holiday" or "They have holidayS" .
I am confused, "en juillet et aout" is acceptable in the answer as per above, but when I used it the sentence: "Ils sont en vacances en juillet et aout" this was marked wrong ("pendant" was proposed).
Perhaps because you used "they are on vacation ..." rather than "they have vacation ..." The first may prompt " during July and August" which would equate to the proposition you were presented with.
Ils sont en vacances pendant juillet et août = "They are on vacation during July and August"
I answered exactly as per the "given" answer but the app will not allow me to continue?
In English it would be far more usual to say we are having (or taking) a holiday or we are going on our holidays. Vacation sounds american and more unusual to be used in the UK.