用竖式计算下列各题.((2)题要验算)(1)3.86+8.34=(2)50.5﹣21.06=验算.
8×5÷4
500×6÷5
45÷5×3
3×8÷6
口算。9×6= 7×8= 9×5= 8×4= 9×5+5=6×3= 6×6= 7×6= 3×8= 8×7―20=8×6= 7×4= 6×5= 9×4= 6×9+9=9×2= 8×5= 7×1= 2×6= 7+7+7+7=