catkittycats

1. Total ways to select 3 people from 5 couples (10 people) = 10C3 = 120
Ways to ensure that a couple is selected to the committee = 5C1*8C1 = 40

Ways to ensure that no couple is selected to the committee = 120-40=80

catkittycats

Let the total newspaper sold be 100.

Newspaper A sold = p
Newspaper B sold = 100-p
Total revenue = p*1+(100-p)*1.25
So revenue from paper A = p*1 = p
Revenue percentage from paper A = (p/(p+(100-p)*1.25))*100
This is equal to r
thus
(p/(p+(100-p)*1.25))*100 = r

=> r = 100p/(125-0.25p)
Multiplying by 4 in numerator and denominator on RHS, we get
r = 400p/(500-p)