From a group of 7 men and 6 women, five persons are to be selected to form a committee so that at least 3 men are there on the committee. In how many ways can it be done?

We may have (3 men and 2 women) or (4 men and 1 woman) or (5 men only). 

Required number of ways=  $7C3*6C2+7C4*6C1+7C5$ = 756.