(8.5+1.5)x0.75=10x0.75=7.5
=8.5x0.75+1.5x0.75=(8.5+1.5)x0.75=10x0.75=7.5
8.5x3/4+1.5x0.75=(8.5+1.5)x3/4=10×3/4=7.5
(8.5+1.5)乘0.7 5=7.5