In a pet shop, the ratio of the number of kittens to the total number of puppies and rabbits was 2:5. The ratio of the number of puppies to the number of rabbits was 9:1. There were 15 more puppies than kittens. After some kittens were added to the shop, 2/5 of the pets were kittens. How many kittens were added?
(1) 8
(2) 12
(3) 15
(4) 20
k/(p+r) = 2/5
p/r = 9/1
p = k+15
If x kittens were added, then
(k+x)/(k+p+r) = 2/5
Solve these to find x