The upper limit for the function f(x) = x3 - 3x 2 - 2x + 15 is 3 4 5

Three numbers x, y, and z are in the ratio 2: 7: 8. if 12 is subtracted from y, then three numbers form a geometric sequence (in the order x, y–12, z). find x, y, and z. there are 2 sets.