Question

Show how to solve 6/15=2/?

Answer 1

There are two way sof doing this question: 
 1st solution  is : 
 6/15 = 2/5
because 6/15 is divisible by 3 and it is done by this form : 
     3 X 2 = 6
       and
    3 X 5 = 15
2nd solution is:
6/15 = 2/?
here we suppose that the missing value is x:
 6/15 = 2/x 
 you shift the denominators and then  multiply them by the their numerators:
 6 * x = 15 * 2
      6x = 30
 now you divide 6 on both sides:
 6x/6 = 30/6
      x = 5

Answer 2

6 / 15 = 2 / x

6x = 30

x = 30 / 6 = 5