Respuesta :
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.
