( 21/20--1/4)除以x=7/8

( 21/20--1/4)除以x=7/8
(21/20-5/20)÷x=7/8
16/20÷x=7/8
4/5÷x=7/8
x=4/5÷7/8
x=4/5*8/7
x=32/35