les semaines
Huit semaines. Please not that all numbers must be written out in French.
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trois semaines
Deux semaines
Not exactly see you in a few weeks but, à bientôt means see you soon. Vous voir en quelques semaines, I believe means see you in a few weeks. You can say Salut or au revoir to say goodbye.
It depends what you want to say. For example, if you want to say there's three weeks left before Christmas, say "Il reste trois semaines"
Je suis allé pendant deux semaines
Vacation, in French “Les Vacances” (always plural), is at the heart of the French culture. With 5 weeks of paid vacation for French employees, and a total of 16 weeks of vacation for French school students, France sure values her holidays.
je suis à Bruxelles pour deux semaines
quelques semaines plus tard
french students usually have about 7 weeks of holidays a year.
two weeks = deux semaines