3:4/7+1/6-3/7
=4/7-3/7+1/6
=1/7+1/6
=13/42
2-7/9-2/9
=2-(7/9+2/9)
=2-1
=1
1/4+(2/5+3/4 )
=1/4+3/4 +2/5
=1+2/5
=1又2/5
3/5+7/8+2/5
=3/5+2/5+7/8
=1+7/8
=1又7/8
7/9-(1/9+1/3)
=7/9-1/9-1/3
=2/3-1/3
=1/3
5/6-3/10+1/6-3/10
=(5/6+1/6)-(3/10+3/10)
=1-3/5
=2/5
4:⑴ 1-1/5-1/10
=1-2/10-1/10
=7/10
⑵ 1/2-1/5-1 |