[3.6-(1.6+2/9)-7/9]x3/7
=[(3.6-1.6)-(2/9+7/9)]×3/7
=(2-1)×3/7
=3/7
8/9X[3/4-(7/16-0.25)]
=8/9×(3/4+0.25-7/16)
=8/9×(1-7/16)
=8/9×9/16
=1/2是简便计算吗要简便的en