First factor the numerator and denominator.

64 =  2 · 2 · 2 · 2 · 2 · 2

68 = 2 · 2 · 17 

The GCF is the product of the common prime factors in each term.

GCF = 2 · 2 = 4 \ \

Divide the numerator and the denominator by GCF.

               (Simplify)

Simplifest form of the fraction is .