To simplify a fraction you find the GCF (Greatest Common Factor) of the numerator and denominator.
To find the GCF find all the factors of both numbers and the factor that is highest is your GCF.
Example: 6/15
6: 1, 2, 3, 6
15: 1, 3, 5, 15
Three is the GCF in this example.
To simplify, divide the numerator and denominator by the GCF.
Example: 6/15
6/3 = 2
15/3 = 5
6/15 = 2/5