It would've been better if you had waited..
If I were you,I would go home immediately.
I will answer your question if I can.
He would've told you if you had asked him.
If you would have driven more carefully,you wouldn't have an accident.
If the child is good, he gets a bar of chocolate.
He will be at the airport in time if he leaves now.
If I'll see him, I would speak to him.
If he had written a letter to me, I would've answered it.
You will be sick if you eat so much.