1.7/8-1/6+5/12
=7/8-(1/6-5/12)
=7/8+1/4
=9/8
2.8/9-(2/3-1/6)
=8/9-1/2
=16/18-9/18
=7/18
3.5/9-8/15+7/9-7/15
=12/9-1
=1/3
4.5/7(4/7+1/9)
=(5/7)*(43/63)
=215/441
1.7/8-1/6+5/12
=7/8-(1/6-5/12)
=7/8+1/4
=9/8
2.8/9-(2/3-1/6)
=8/9-1/2
=16/18-9/18
=7/18
3.5/9-8/15+7/9-7/15
=12/9-1
=1/3
4.5/7(4/7+1/9)
=(5/7)*(43/63)
=215/441