6=x-21

Solution for 6=x-21 equation:

Simplifying
6 = x + -21

Reorder the terms:
6 = -21 + x

Solving
6 = -21 + x

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Add '-1x' to each side of the equation.
6 + -1x = -21 + x + -1x

Combine like terms: x + -1x = 0
6 + -1x = -21 + 0
6 + -1x = -21

Add '-6' to each side of the equation.
6 + -6 + -1x = -21 + -6

Combine like terms: 6 + -6 = 0
0 + -1x = -21 + -6
-1x = -21 + -6

Combine like terms: -21 + -6 = -27
-1x = -27

Divide each side by '-1'.
x = 27

Simplifying
x = 27