列竖式计算.783÷6= 752÷7= 299÷9= 640÷8=
9-4= 9-5= 4+5=
10-4= 10-6= 4+6=
5+2= 7-5= 7-2=
4+1= 5-1= 5-4=
2+6= 8-6= 3+3= 6-3=