So basically it sounds like it wants you to make the denominators match.
Here's an example:
3/4 and 1/2
First you would find the Least Common Multiple (LCM), which of these two numbers is 4.
3/4 and 2/4 Then you would multiply the denominator the same amount you multiplied the denominator.
and voila! 3/4 and 2/4 have matching denominators
Please ask questions if you are still confused!