all you have to do is
difference for example:
3/4. 4,(8),12,16,20,24
- 1/8. (8),16,24,32,40
if you see the same small number circle them then that will be you denominator then in the 4 count the number 8 is in the 2* place so you multiply 2 by 3 then in the 8 count 8 is in the 1* so you multiply 1 by 1 then once you got those you subtract 6 by 1 that makes 5 so your answer is 5/8.