2.5x7+2.5x(-2)+2.5x3 (1又3/4-7/8-7/12)x(-1又1/7)

问题描述:

2.5x7+2.5x(-2)+2.5x3 (1又3/4-7/8-7/12)x(-1又1/7)

17.5-5+2.5=15