Which expresses 6y : 9y in its simplest form?
a. 9 : 6
b. 2 : 3
c. 6 : 9
d. 3 : 2

This problem is an example of ratio and proportion. You are given 6y:9y. You are required to convert this into its simplest form. The 6y:9y is also equivalent to 6y/9y. The ‘y’ variable can be eliminated since it has the same exponent and base. You are left with 6/9. The common factor for 6 and 9 is 3 so divide each number by 3. So 6/3 is 2 and 9/3 is 3. You get 2/3. This is its simplest form.