Escreva no passado:

A) I can speak english.

I could speak English.

B) She can write the letter.

She could write the letter.

C) Mr.Porter can repair the watch.

Mr. Porter could repair the watch.

D) You can read well.

You could read well.

E) She can go with you.

She could go with you.

F) They can jump over that box.

They could jump over the box.

Observação:

O tempo passado do verbo "can" pode ser expresso por "could", porém precisamos, geralmente, de um complemento na sentença para indicar isso, senão o sentido pode mudar.

Exemplo: I can read (Eu posso ler) -> I could read (Eu poderia ler) -> I could read when I was 6 (Eu podia ler quando eu tinha 6 anos).