Let's break it down:
We need an LCM, a least common multiple, so it's easier to subtract
3 1/4x + 7 1/14
-
1/8x - 2 5/7
3 1/4 is equivalent to 3 2/8
2 5/7 is equivalent to 2 10/14
3 2/8x + 7 1/14 or you can break it down to two parts also
- 3 2/8x - 1/8x = 2 1/8x
1/8x - 2 10/14 7 1/14 - (-2 10/14) = 9 11/14
------------------ - - = +
2 1/8x + 9 11/14
