math

You forgot the squared. if you meant 24 x^2 y / 40 x y ^2 it would be 24/40 * x^2/x * y/y^2 = 3/5 * x* 1/y = 3x / 5y.
If you meant 24 x^2 y / 40 (xy)^2 then you would get 24/40 *x^2/x^2 * y/y^2 = 3/5y

edit: "deleted because incorrect"