Final answer:
The reverse of multiplying by 9 is dividing by 9.
Step-by-step explanation:
In mathematics, the reverse of multiplying by 9 is dividing by 9.
To understand this, let's take an example:
If we have a number, let's say 36, and we multiply it by 9, we get 36 * 9 = 324.
To reverse the process, we divide 324 by 9 to get the original number: 324 ÷ 9 = 36.
Therefore, the answer is C. Divide by 9.