When adding or subtracting fractions we need to work out the LCD (lowest common denominator). That means we need to find the smallest number that the denominators of the fractions all divide into without a remainder. Sometimes this is easy to do by factorising each denominator so we can see what numbers make it up. In your case, we see that 56 is one denominator that can be split into 8*7, and it just so happens that the other fraction has a denominator of 7. How many 56ths do we need to make 1/7? We need 8. So for 5/7 we need 5 times as many, so we need 40. Now that we have both fractions sharing a common basis, we can do the sum. 13/56 + 5/7 is the same as 13/56 + 40/56. That makes 53/56 just by adding the numerators. It's like adding 13 apples to 40 apples, where an apple is represented by a 56th. To help you with this sort of problem when the denominators have no common factors just multiply the denominators together to create the LCD. Also when you've finished the sum, check to see if the result cancels down to a simpler fraction because numerator and denominator share a common factor.