简便计算5/1【五分之一】×4/1+75%×20%（2/3-24/5-24/7）×361÷（3/2-6/1）×75%不是

1、原式=（1/5)x(1/4)+(3/4)x(1/5)
=(1/5)x[(1/4)+(3/4)]
=(1/5)x1
=1/5
2、原式=36x(2/3)-36x(5/24)-36x(7/24)
=24-(15/2)-(21/2)
=24-18
=6
3、原式=1÷[(2/3)x(3/4)-(1/6)x(3/4)]
=1÷[(1/2)-(1/8)]
=1÷（3/8)
=8/3