-9 = -21 + x

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4

To solve the equation, we need to first isolate the variable x. We can do this by subtracting -21 from both sides and then dividing by 4.

-9 + 21 = x / 4

12 = x / 4

To solve for x, we can multiply both sides of the equation by 4.

12 * 4 = x

48 = x

Therefore, x is equal to 48.