What is; 6 5/8 + d= 7 15/8: d= ?
6 5/8 + d= 7 15/8 ..... 7 15/8 = 7 + 1 + 7/8 = 8 7/8
So we have
6 5/8 + d= 8 7/8 subtract 6 5/8 from both sides
d = 8 7/8 - 6 5/8 =
d = 2 2/8 = 2 1/4