Let x and y represent the two angles. .. x + y = 90 . . . . . . two angles are complementary .. x -2y = 15 . . . . . . one angle is 15 more than twice the other (y = smaller angle)
Subtract the second equation from the first. .. (x +y) -(x -2y) = (90) -(15) .. 3y = 75 .. y = 25