Answer :
The factors of 45 are
1, 3, 5, 9, 15, 45
The factors of 60 are
1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
The common factors are the factors shared by both numbers, so
1, 3, 5, 15
1, 3, 5, 9, 15, 45
The factors of 60 are
1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
The common factors are the factors shared by both numbers, so
1, 3, 5, 15