5/8÷7/20*4*7/10
=5/8×20/7×4×7/10
=5
5/7*34*7*2/17
=5/7×7×34×2/17
=5×4
=20
88*16/87
=（87+1）×16/87
=87×16/87+1×16/87
=16+16/87
=16又16/87
（1/4+1/5）*4*5
=1/4×4×5+1/5×4×5
=5+4
=9