Question 937069
class consists of 20 boys and 25 girls
Selecting seven members
a {{{  (20C2)(25C5) + (20C3)(25C4) + (20C4)(25C3) + (20C5)(25C2) + (20C6)(25C1) + (20C7)(25C0)}}} 
b (Like above)
c {{{(20C4)(25C3)}}}