Help please I don’t know the answer

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

Can someone explain to me how to do

Abag contains 10 white golf balls and 6 striped golf balls. a golfer wants to add 112 golf balls to the bag. he wants the ratio of white to striped gold balls to remain the same. how many of each should he add?