15 1/4 - 115/8

You can individually subtract 11 from 15 and 5/8 from 1/4.

 

Note that you have to convert 1/4 into something #/8 to have common denominators. Since 4*2 = 8, 1*2 = 2 --> 2/8.

 

15 - 11 = 4

2/8 - 5/8 = -3/8

 

So, we need to get common denominators again. So, 4/1 --> #/8...

 

4*8 = 32

1*8 = 8

 

32/8 - 3/8 = 29/8.