8/9×4/5+8/9
=8/9×4/5+8/9×1.........改写
=8/9×（4/5+1）.........乘法的分配律合并
=8/9×9/5
=8/5
8/9×4/5+8/9=8/9×(4/5+1)=8/9×9/5=8/5=1.6
8/9×4/5+8/9=8/9×（1+4/5）=8/9×9/5=8/5=1又3/5
