"En verano no nos ponemos las chaquetas."
Translation:In summer we don't put on jackets.
When using the preposition en to talk about means of transportation and seasons, you should omit the definite article. "Trabajo en verano" - "I work in the summer" "Ella viaja en autobús" - "She travels by bus"
I was curious about the las article as well. It is clearly not talking about all jackets (In summer we don't put on all jackets) but rather any jackets (In summer we don't put on any jackets). So I would assume that las would need to have an English translation (the or our); however, their accepted answer is "put on jackets." I'm so confused now.