What ratio is equivalent to 21/56?

A) 4/7

B) 12/15

C) 12/32

D) 4/12

21/56 is equivalent to 3/8 then multiply by 4 to get C.) 12/32

There are a couple of methods to solve this problem however; there is no solution for this problem due to the answer selection being incorrect. For instance, I teach, "what you do to one side, you do to the other, or, what you do to the top, you do to the bottom". Since 21 is limited to a multiple of 3 or 7, and 56 is limited to a multiple of 2, 4, or 7, there is no solution using the answer choices.