The easiest way would be to subtract (3 and 7/8) from (7) to get (3 and 1/8). Another way would be to convert (3 and 7/8 to 31/8) and (7 to 56/8) and then subtract straight acrossed the top to get (25/8 which when converted to a mixed number is 3 and 1/8). If i confused you or i need to better explain don't be afraid to ask.
