Can you explain a little more on equivalent fractions with common denominator 3/4, 2/3, 7/8 thank you verry much.

First find the common denominator. Here are the multiples of 8:

8, 16, 24, 32, 40

Which of those numbers is divisible by both 3 and 4?

This site has a good explanation.

http://www.mathsisfun.com/equivalent_fractions.html