Question

5/7+2/7+3/8用递等式计算

递等式计算.（能用简便方法计算的要用简便方法计算）
1又5/7+2/3+3又1/3+2又2/7、1又1/2-3/4+5/6、9又3/5-2又1/6-3又5/6+2又2/5、3/7+7/8+4/7-1/8、2又3/5-（2/9+3/5）、2.8+1/2-1.6

Answer 1

1又5/7+2/3+3又1/3+2又2/7
=1+5/7+2/3+3+1/3+2+2/7
=1+3+2+5/7+2/7+2/3+1/3
=6+1+1
=8
1又1/2-3/4+5/6
=1+1/2-3/4+5/6
=1+6/12-9/12+10/12
=1+7/12
=1又7/12
9又3/5-2又1/6-3又5/6+2又2/5
=9+3/5-2-1/6-3-5/6+2+2/5
=9-2-3+2+3/5+2/5-(1/6+5/6)
=6+1-1
=6
3/7+7/8+4/7-1/8
=3/7+4/7+7/8-1/8
=1+6/8
=1+3/4
=1又3/4
2又3/5-（2/9+3/5）
=2+3/5-2/9-3/5
=2-2/9+3/5-3/5
=1+9/9-2/9+0
=1+7/9
=1又7/9
2.8+1/2-1.6
=2.8-1.6+1/2
=1.2+0.5
=1.7