楼主说是3/4的
（7/10+3/4）×5
=7/10×5+3/4×5
=7/2+15/4
=29/4
135×8/9×3/4
=135×（8/9×3/4）
=135×2/3
=90
6/11×7/8-6/8×6/11
=6/11×（7/8-6/8）
=6/11×1/8
3/44