21÷(1/3+2/5)÷9/11= 21÷[(5/15+6/15)×(9/11)]= 21÷[(11/15)×(9/11)]= 21÷(9/15)=21÷(3/5)=21×(5/3)=35
21÷(1/3+2/5)÷9/11 =21÷(5/15+6/15)÷9/11 1*5/(3*5)+(2*3)/)5*3) = 21÷[(11/15)×(9/11)] = 21÷(9/15)=21÷(3/5)=21×(5/3)=35