十五分之二+一有九分之七=?(求简便)

问题描述:

十五分之二+一有九分之七=?(求简便)

2/15+1又7/9
=2/15+1+1-2/9
=2-(2/9-2/15)
=2-2×(1/9-1/15)
=2-2×2/45
=2-4/45
=1又41/45