1、75/100×4/15+80/100÷4/7
=3/4×4/15+4/5×7/4
=1/5+7/5
=8/5
2、3/4×25/2+5.875×75/100+0.75
=3/4×25/2+47/8×3/4+3/4
=3/4×（25/2+47/8+1）
=3/4×155/8
=465/32
3、1/5÷[(2/3+1/5)×0.75]
=1/5÷[13/15×3/4]
=1/5×20/13
=4/13
4、25/100×7/20+5/12×0.75
=1/4×7/20+5/12×3/4
=7/80+5/16
=32/80
=2/5