240÷40 300÷60 490÷70 400÷50 800÷80 540÷90
123×5.67+8.77×567= .
80×16×25×125= .
(562×397)÷(281×397)= .
29×12+29×13+29×25+29×10= .
14.8×6.3﹣6.3×6.5+8.3×3.7= .