Question

8=56 7=42 6=30 5=20 4=

Answer 1

here, the equation x=x(x-1) is being followed
so, 4=4(4-1)=4x3=12

Answer 2

4=12
see the example
8*7=56
7*6=42
6*5=30
5*4=20
4*3=12