1)l (do) the homework if the teacher had explained it.
have did ,would, will, have done
2) lf the (wait) for 10 minutes, he would have seen the pop star
have, waited, wait, had

1) I would have done

2) had waited

1)l would have done the homework if the teacher had explained it.

2) lf he/they had waited for 10 minutes, he would have seen the pop star.