x+21=3x-9

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Solution for x+21=3x-9 equation:


Simplifying
x + 21 = 3x + -9

Reorder the terms:
21 + x = 3x + -9

Reorder the terms:
21 + x = -9 + 3x

Solving
21 + x = -9 + 3x

Solving for variable 'x'.

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

Add '-3x' to each side of the equation.
21 + x + -3x = -9 + 3x + -3x

Combine like terms: x + -3x = -2x
21 + -2x = -9 + 3x + -3x

Combine like terms: 3x + -3x = 0
21 + -2x = -9 + 0
21 + -2x = -9

Add '-21' to each side of the equation.
21 + -21 + -2x = -9 + -21

Combine like terms: 21 + -21 = 0
0 + -2x = -9 + -21
-2x = -9 + -21

Combine like terms: -9 + -21 = -30
-2x = -30

Divide each side by '-2'.
x = 15

Simplifying
x = 15

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