Respuesta :

When the denominators are different numbers on the bottom of the fraction bar

for example:
[tex] \frac{1}{2} + \frac{1}{3} [/tex]
2 and 3 are different, so you would need to find the Greatest Common Factor (GCF) to get them to have the same denominator.

(sorry, I am a bad explainor)
When the two bottom number in a fraction are different