надо поставить в отрицательную, во и в утвердительную форму​

They bought a new car last week.

They didn't buy a new car last week.

Did they buy a new car last week?

They bought a new phone one day. (во когда, поэтому добавила one day - однажды, хотя можешь оставить до phone)

They didn't buy a new phone. (здесь подразумевается, что не купили - не купили никогда, поэтому one day и другие обозначения времени не нужны)

When did they buy a new phone?

He was at the zoo last weekend.

He wasn't at the zoo last weekend.

Was he at the zoo last weekend?

Last weekend he was somewhere. (был где-то, опять же, потому что во где)

Last weekend he wasn't anywhere. (нигде)

Where was he last weekend?

Объяснение:

They bought a new car last week. They didn't buy a new car last week. Did they buy a new car last week?

They bought a new phone yesterday. They didn't buy a new phone last month. When did they buy a new phone?

He was at the zoo last weekend. He wasn't at the zoo last weekend. Was he in zoo last week?

He was at cafe last weekend. He wasn't at home last weekend. Where was he last weekend?