Step One: Find the greatest common factor of the numerator and the denominator.
Factors of 8: 1, 2, 4, 8
Factors of 18: 1, 2, 3, 6, 9, 18
Common Factors: 1, 2
Greatest Common Factor: 2
Step Two: Divide the numerator and denominator by the GCF.
8 ÷ 2 = 4
18 ÷ 2 = 9
Step 3: Write as a fraction.
[tex] \frac{4}{9} [/tex]