Answer:
15
Step-by-step explanation:
We can find the greatest common factor by listing the factors of the 2 numbers, that is
Factors of 15 are 1, 3, 5, 15
Factors of 45 are 1, 3, 5, 9, 15, 45
The common factors are 1, 3, 5, 15
The greatest common factor is 15
