(1)( 1 2 + 1 3 )÷( 1 2 - 1 3 )= 5 6 ÷ 1 6 =5答:商是5.(2)设这个数是x3x-45× 3 5 =33x-27+27=3+27 3x÷3=30÷3 x=10答:这个数是10.