Solve 12x − 9 = −105

The solution of 12x − 9 = −105 is x = -8.

12x - 9 = -105\ \Rightarrow\ x = -8

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The lines y = 12x − 9 and y = -105 meet at x = -8. 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.
$12x - 9 = -105$
2
Add 9 to both sides:
$12x - 9 + 9 = -105 + 9 \ \Rightarrow\ 12x = -96$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-96}{12} \ \Rightarrow\ x = -8$
4
Check: put x = -8 back into the equation.
$12\cdot(-8) - 9 = -96 - 9 = -105 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 9 = -105\ \Rightarrow\ x = -8 \]
\[ 12x - 9 = -105 \]
\[ 12x - 9 + 9 = -105 + 9 \ \Rightarrow\ 12x = -96 \]
\[ \frac{12x}{12} = \frac{-96}{12} \ \Rightarrow\ x = -8 \]
\[ 12\cdot(-8) - 9 = -96 - 9 = -105 \checkmark \]

Trying values of x in 12x − 9 = −105

x	12x − 9	Equals -105?
-10	-129	no
-9	-117	no
-8	-105	yes
-7	-93	no
-6	-81	no

Questions

What is x in 12x − 9 = −105?

The solution of 12x − 9 = −105 is x = -8.

How do you solve 12x − 9 = −105?

Add 9 to both sides to get 12x = -96, then divide both sides by 12 to get x = -8.

How do I check the answer?

Replace x by -8: 12(-8) − 9 = -105, which is -105.

Solve 12x − 9 = −105

How to work it out

Trying values of x in 12x − 9 = −105

Questions

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