Answer:
(6*5) - (3*7)
Explanation:
The cubic grid represents the overall blocks.
Since this is true we would take into account that each block represents a number.
Since the right grid is larger it would be easier to count the left grid. Which comes out to 21.
By doing this we can check which answer holds the correct equation. By cross checking since 7 * 3 is the only one in the answer choices that comes out to 21 we can safely assume that C is the correct answer.