Solve 12x + 9 = −99

The solution of 12x + 9 = −99 is x = -9.

12x + 9 = -99\ \Rightarrow\ x = -9

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The lines y = 12x + 9 and y = -99 meet at x = -9. 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 addition, then the multiplication.
$12x + 9 = -99$
2
Subtract 9 from both sides:
$12x + 9 - 9 = -99 - 9 \ \Rightarrow\ 12x = -108$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-108}{12} \ \Rightarrow\ x = -9$
4
Check: put x = -9 back into the equation.
$12\cdot(-9) + 9 = -108 + 9 = -99 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 9 = -99\ \Rightarrow\ x = -9 \]
\[ 12x + 9 = -99 \]
\[ 12x + 9 - 9 = -99 - 9 \ \Rightarrow\ 12x = -108 \]
\[ \frac{12x}{12} = \frac{-108}{12} \ \Rightarrow\ x = -9 \]
\[ 12\cdot(-9) + 9 = -108 + 9 = -99 \checkmark \]

Trying values of x in 12x + 9 = −99

x	12x + 9	Equals -99?
-11	-123	no
-10	-111	no
-9	-99	yes
-8	-87	no
-7	-75	no

Questions

What is x in 12x + 9 = −99?

The solution of 12x + 9 = −99 is x = -9.

How do you solve 12x + 9 = −99?

Subtract 9 from both sides to get 12x = -108, then divide both sides by 12 to get x = -9.

How do I check the answer?

Replace x by -9: 12(-9) + 9 = -99, which is -99.

Solve 12x + 9 = −99

How to work it out

Trying values of x in 12x + 9 = −99

Questions

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