126 1/4 = 126 3/12 = 125 15/12
- 78 2/3 = - 78 8/12 = - 78 8/12
--------------------------------------...
47 7/12
1) Find the lowest common denominator (LCD) for the fractions. In this case, 12 is the LCD.
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 it's confusing to subtract 8/12 from 3/12, you need to borrow one from the 126. Doing so is the same as taking 12/12 from 126. This changes to 125, and the 12/12 adds to the 3/12 making it 15/12.
4) Subtract 8/12 from 15/12 to get 7/12.
5) Subtract 78 from 125 to get 47.
6) The answer is 47 7/12.