7/8h+1 1/4=6==> Change the mixed fraction to improper.
7/8h+5/4=6===> Subtract 5/4 from both sides.
7/8h+5/4-5/4=6-5/4
7/8h=19/4===> Multiply both sides by the reciprocal of 7/8, which is 8/7
(8/7)7/8h=19/4(8/7)
56/56h=152/28
1h=38/7
h=5 3/7
Thus the answer is choice B.