Question

how to rewrite a fraction so that the denominators are equal

Answer 1

First you must find a denominator that is common to all your fractions, then convert each fraction to use that denominator.

Answer 2

For example:
\[\frac{5}{6} + \frac{4}{15} = \frac{5}{6}\cdot \frac{5}{5} + \frac{4}{15}\cdot \frac{2}{2} = \frac{25}{30} + \frac{8}{30} = \frac{33}{30} = \frac{11}{10}\]