Ok, It's hard to explain so I'll use an example. 1/5 + 2/15 now you try to find a number that goes into both for this example it would be 3 3*5=15 and then that equals the 2/15 so you then multiply 3 by the numerator getting the fraction 3/15 + 2/15 with the answer of 5/15 which can be reduced to 1/3