5/12--(3/4--3/5)
问题描述:
5/12--(3/4--3/5)
怎么是负数?
答
5/12--(3/4--3/5)
=5/12--(15/20-12/20)
=5/12-3/20
=25/60-9/60
=16/60
=4/15