The answer is twelve (12).
Let us use this equation: 4x-36= 12
x stands for the missing number.
To solve for x, we will transfer the -36 to the side of 12, and it will look like this: 4x= 12+36 (NOTE: Once we transfer a number on the other side, their signs will change too. For example, the -36 became positive 36 when it was transferred to the side of the 12)
Then, 4x= 48, divide both sides by 4 so that the x will remain. 48/4= 12.
Therefore, x=12
