What number should replace the question mark?

Question

Answer 1

Find the opposite value according to:
12 x 4 - 4 x 4 = 32
17 x 4 – 4 x 4 = 52
21 x 4 – 4 x 4 = 68
10 x 4 – 4 x 4 = 24
Hence the number 24 will replace the question mark.