Brandon has cans of both diet soda as well as regular soda. The ratio of diet soda to regular soda is 3 to 7. He has 12 more cans of soda than diet. How many cans of diet soda does he have left?  Choose the most appropriate option:
A) 6  B) 7  C) 8  D) 9  E) 10
Let x equal the cans of diet soda, and y equal the cans of regular soda.   Since we want to solve for x (cans of diet soda), we convert the ratio from 3/7 to 7/3.   So, we know that y = 7/3x.   We also know that y = x + 12.   We can simplify:   x + 12 = 7/3x   To isolate x, we get:   4/3x = 12   And to solve for x, we get:   x = 9   Answer: 9
<result>D</result>
Brandon has cans of both diet soda as well as regular soda. The ratio of diet soda to regular soda is 3 to 7. He has 12 more cans of soda than diet. How many cans of diet soda does he have left?