Para algo que era verdade antes, mas não é mais, diga used to + o verbo no infinitivo.
used to + verbo no infinitivo
I used to play tennis. (but I stopped)
Amina used to live near the harbor. (now she lives downtown)
We used to walk to school every day.
Not "I use to play tennis." — say "I used to play tennis.". Aqui tem o -d: used to. Significa que você fazia isso antes, mas não faz mais.
Experimente: Amina ___ live near the harbor, but now she lives downtown. (used to / use to / uses to) Resposta: used to — Para algo que era verdade antes e mudou, use used to, com o -d. "Use to" (sem -d) e "uses to" não são a forma de passado aqui: she used to live there.
didn't use to
Para dizer que algo não era verdade antes, diga didn't use to + o verbo no infinitivo. Depois de didn't, tire o -d: fica use to, não "used to".
I didn't use to like coffee. (now I do)
She didn't use to study hard.
We didn't use to have a car.
Not "I didn't used to like coffee." — say "I didn't use to like coffee.". Depois de didn't, não tem -d: didn't use to.
Experimente: I ___ like coffee, but now I drink it every day. (didn't use to / didn't used to / don't use to) Resposta: didn't use to — As palavras estão certas, mas depois de didn't não tem -d: didn't use to (não "didn't used to"). E para o passado você precisa de didn't, não "don't".
Did you use to ...?
Para perguntar, comece com Did + a pessoa + use to + o verbo no infinitivo. De novo, depois de Did, é use to sem -d.
Did you use to play tennis?
Did she use to live here?
Where did you use to work?
Experimente: ___ you use to play tennis? (Did / Do / Were) Resposta: Did — Para perguntar sobre o passado, comece com Did: Did you use to play tennis? "Do" é para o presente, e "Were" é para o que alguém era, não o que fazia.
Experimente: She ___ smoke, but she ___ exercise much — she never went to the gym back then. (used to … didn't use to / use to … didn't used to / used to … didn't used to) Resposta: used to … didn't use to — Sozinho, mantém o -d: used to smoke. Mas ao lado de didn't, o -d some: didn't use to. O -d aparece na frase simples e some depois de did/didn't.