Solve 12x − 9 = −129

The solution of 12x − 9 = −129 is x = -10.

12x - 9 = -129\ \Rightarrow\ x = -10

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The lines y = 12x − 9 and y = -129 meet at x = -10. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$12x - 9 = -129$
2
Add 9 to both sides:
$12x - 9 + 9 = -129 + 9 \ \Rightarrow\ 12x = -120$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-120}{12} \ \Rightarrow\ x = -10$
4
Check: put x = -10 back into the equation.
$12\cdot(-10) - 9 = -120 - 9 = -129 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 9 = -129\ \Rightarrow\ x = -10 \]
\[ 12x - 9 = -129 \]
\[ 12x - 9 + 9 = -129 + 9 \ \Rightarrow\ 12x = -120 \]
\[ \frac{12x}{12} = \frac{-120}{12} \ \Rightarrow\ x = -10 \]
\[ 12\cdot(-10) - 9 = -120 - 9 = -129 \checkmark \]

Trying values of x in 12x − 9 = −129

x	12x − 9	Equals -129?
-12	-153	no
-11	-141	no
-10	-129	yes
-9	-117	no
-8	-105	no

Questions

What is x in 12x − 9 = −129?

The solution of 12x − 9 = −129 is x = -10.

How do you solve 12x − 9 = −129?

Add 9 to both sides to get 12x = -120, then divide both sides by 12 to get x = -10.

How do I check the answer?

Replace x by -10: 12(-10) − 9 = -129, which is -129.

Solve 12x − 9 = −129

How to work it out

Trying values of x in 12x − 9 = −129

Questions

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