How to Use Third Conditional Sentences
Third conditional sentences are used to explain that present circumstances would be different if something different had happened in the past. Look at the following examples:
Example: If you had told me you needed a ride, I would have left earlier. – Если бы ты сказал мне, что тебя нужно подвезти, я бы ушел раньше.
Example: If I had cleaned the house, I could have gone to the movies. – Если бы я убрался дома, я мог бы пойти в кино.
Explanation: With third conditional sentences, do not use a modal auxiliary verb in the if-clause.