3 I failed my exams. I should have studied harder.

Ответ (EN):

1. I wish I had studied harder.
2. If I had studied harder, I wouldn't have failed my exams.

Перевод (RU):

1. Я бы хотел усерднее учиться.
2. Если бы я учился усерднее, я бы не провалил экзамены.