Solve 12x − 9 = −45

The solution of 12x − 9 = −45 is x = -3.

12x - 9 = -45\ \Rightarrow\ x = -3

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The lines y = 12x − 9 and y = -45 meet at x = -3. 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.
$12x - 9 = -45$
2
Add 9 to both sides:
$12x - 9 + 9 = -45 + 9 \ \Rightarrow\ 12x = -36$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-36}{12} \ \Rightarrow\ x = -3$
4
Check: put x = -3 back into the equation.
$12\cdot(-3) - 9 = -36 - 9 = -45 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 9 = -45\ \Rightarrow\ x = -3 \]
\[ 12x - 9 = -45 \]
\[ 12x - 9 + 9 = -45 + 9 \ \Rightarrow\ 12x = -36 \]
\[ \frac{12x}{12} = \frac{-36}{12} \ \Rightarrow\ x = -3 \]
\[ 12\cdot(-3) - 9 = -36 - 9 = -45 \checkmark \]

Trying values of x in 12x − 9 = −45

x	12x − 9	Equals -45?
-5	-69	no
-4	-57	no
-3	-45	yes
-2	-33	no
-1	-21	no

Questions

What is x in 12x − 9 = −45?

The solution of 12x − 9 = −45 is x = -3.

How do you solve 12x − 9 = −45?

Add 9 to both sides to get 12x = -36, then divide both sides by 12 to get x = -3.

How do I check the answer?

Replace x by -3: 12(-3) − 9 = -45, which is -45.

Solve 12x − 9 = −45

How to work it out

Trying values of x in 12x − 9 = −45

Questions

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