17/30除以（3/5+2乘以1/8）
=17/30÷(3/5+1/4)
=17/30÷17/20
=2/3
1/6x除以1/8=8/9
4/3x=8/9
x=8/9÷4/3
x=2/3
x-40%x=2/5
3/5x=2/5
x=2/5÷3/5
x=2/3
x-5/12=5/42除以5/28
x-5/12=2/3
x=2/3+5/12
x=13/12