Question

9=72 8=56 742 6=30 5=20 3=?

Answer 1

9= 9*8 = 72
8= 8*7 = 56
7= 7*6 = 42
6= 6*5 = 30
5= 5*4 = 20

So, here we understand that we must multiply the number with its previous number.

3= 3*2 = 6