When you would have to use comon multiples to find what both numbers have in common, a short way of finding this would be where (a) is the answer of the equation, (a) would be 2 because 8*2=16 meaning
so when x(8) equals 16 it would mean 8 is multiplied by 2 and so once x(8) is multiplied by 2 y(16) would also have to be multiplied by 2 which is 32 so y =32 I'm sorry if I'm wrong