A x B x C = 0
Where A and B are integers > 10
Any value multiplied by 0 = 0
Therefore C = 0
The factors of 20 are:
1, 2, 4, 5, 10, 20
The factors of 25 are:
1, 5, 25
The factors of 40 are:
1, 2, 4, 5, 8, 10, 20, 40
The common factors are:
1, 5
The Greatest Common Factor:
GCF = 5