8/9*3/4
=3×8/9-2×3/4
=8/3-3/2
=7/6
5/6*（8/9*3/4）
=5/6*7/6
=3×5/6-2×7/6
=1/636又19/23+63又4/23*0.125+0.5*63又4/23+63又4/23*3/8