Answer:
Simplifying
x = 2x + -21
Reorder the terms:
x = -21 + 2x
Solving
x = -21 + 2x
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '-2x' to each side of the equation.
x + -2x = -21 + 2x + -2x
Combine like terms: x + -2x = -1x
-1x = -21 + 2x + -2x
Combine like terms: 2x + -2x = 0
-1x = -21 + 0
-1x = -21
Divide each side by '-1'.
x = 21
Simplifying
x = 21