用竖式计算下面各题.12.37+8.95= 6.52﹣3.44= 20﹣8.45=9.6+42.17= 28.34﹣7.8= 3.64+0.48=
计算54+99×99+45
计算9+99+999+9999+99999
42:=x:
x-x=
×7+×7