1.

If he read these books

he would know the answer   he will know the answer  No se

2.

You would see the answer

If you look at the blackboard   If you looked at the blackboard   No se

3.

If they bought the crayons,

They colour the picture   They would colour the picture   No se

4.

If you studied,

you would pass the teacher will pass   No se

5.

If you did your homework

You needed a protractor   you would need a protractor  No se