Sorry if I'm wrong - This is how I learned to subtract fractions in the 7th grade
First, I would line up the fractions side-by-side:
5/6 1/8
Then, my teacher would tell me to look at the numerators and subtract those - The answer would be 4
Next, she would say to do the same to the denominators - The answer is 2
4/2 is your answer I believe
Hope this helped! :)