Find missing element in matrix and please explain

Question

20 14 8
10 5 10
5 ? 3

Answer 1

My guess:
20 - 6 = 14 and 14 - 6 = 8
10 - 5 = 5 and 5 - 5 = 0 (didn't get 10 here)
5 - 1 = 4 and 4 - 1 = 3