4/3 - 7/12 + 9/20 - 11/30 + 13/42 - 15/56
= 1 + 1/3 - 1/3 - 1/4 + 1/4 + 1/5 - 1/5 - 1/6 + 1/6 + 1/7 - 1/7 - 1/8
= 1 - 1/8
= 7/8