8-5 3/8-2 5/7
8 - (5 + 3/8) - (2 + 5/7) =
8 - ( 43/8) - ( 19/7) get a common denominator between 7 and 8 = 56
8 - (301 / 56) - ( 152 / 56) =
8 - 453 /56
448 / 56 - 453 / 56 =
-5 /56
