To solve for x, we need to isolate it on one side of the equation.

2x = (-3) - 21

First, we combine the numbers on the right side of the equation:

2x = -24

Next, we divide both sides of the equation by 2 to solve for x:

x = -24/2

Simplifying the right side:

x = -12

Therefore, the solution to the equation is x = -12.