Поставьте глаголы в Past Indefinate,Past Continuous или Past Perfect
 when does coach (to return) the students (to do)  the forth  exercise
the students (to do) all the exercises before the coach( to return)
we(to  discuss )two important questions at last meeting 
the  runner already (to set)a new record before his friend came to the contest 
we(to  discuss )all the problems by 5 o"clock in the evening
when you phoned the students (to do)morning exercises