简便运算:2/12x14+2/12x16+2/16x18+1/20

Question

如题所述

Answer 1

2/12x14+2/14x16+2/16x18+1/20（把第二项的12改为14）
=1/12-114+1/14-1/16+1/16-1/18+1/20
=1/12-1/18+1/20
=1/12-2/18*20
=1/12-1/180
=15/180-1/180
=14/180
=7/90来自：求助得到的回答