In a class, 2/7 of the students have blue eyes. if there are 35 students in the class, how many have blue eyes?

The answer is: 10 (ten).  

        Ten (10) students in the class have blue eyes.

 
(2/7)* (35) = (2/7) * (35/1) ;  

the "7" cancels to a "1"; and the "35" changes to a "5" ; since "35÷7= 5" ;

   (2/1) * (5*1) = (2*5)/(1*1) = 10/1 = 10 .

     The answer is 10 (ten).  
      Ten (10) students in the class have blue eyes.