1) find the lcd the lcd is 12
2)rewrite the fractions 1/4 and 2/3 using 12 as the denominator (second column) you get 3/12 and 8/12
3) since its confusing to subtract 8/12 from 3/12 you need to borrow one form the 126 doing so is the same as taking 12/12 from 126 this change to 125 and the 12/12 adds to the 3/12 making it 15/12
4) subtract 8/12 form 15/12 to get 7/12
5) subtract 78 form 125 to get 47
6) the answer is 47 7/12