Here is a SUPER easy way to compare fractions rather than finding common denominators and all of that stuff. Lets say i want to compare 7/9 and 4/5. Well, if i could write the fraction right on here, seven would be on top. You take your FIRST numerator and multiply it by you SECOND denominator. You write the product BELOW the FIRST fraction. Then, you take the SECOND numerator and multiply it by the FIRST denominator. Write this product BELOW your SECOND fraction. Then, all you have to do is compare these numbers.
Pretty easy, huh? Try it with any set of fractions. My fifth grade math teacher taught my class that a few days ago.