50630000000=亿 420478000000≈亿
A.9 B.900 C.500
12÷3=
1200÷300=
40÷=4
500-213= 10÷10%= 0.25+2.83= 1.25×0.8= 3.7-3.7÷3.7=
92-33= + = × = 9÷ = ( - )×20=