Simplify 15/9

Note, the factors for 15 and 9 are:

 

15: 1, 3, 5, 15

9: 1, 3, 9

 

The greatest common factor is 3, so we divide both the numerator and denominator of 15/9 by 3:

 

15/3 = 5

9/3 = 3

 

We end up with 5/3.