Solve 12x + 9 = −75

The solution of 12x + 9 = −75 is x = -7.

12x + 9 = -75\ \Rightarrow\ x = -7

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The lines y = 12x + 9 and y = -75 meet at x = -7. 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.
$12x + 9 = -75$
2
Subtract 9 from both sides:
$12x + 9 - 9 = -75 - 9 \ \Rightarrow\ 12x = -84$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-84}{12} \ \Rightarrow\ x = -7$
4
Check: put x = -7 back into the equation.
$12\cdot(-7) + 9 = -84 + 9 = -75 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 9 = -75\ \Rightarrow\ x = -7 \]
\[ 12x + 9 = -75 \]
\[ 12x + 9 - 9 = -75 - 9 \ \Rightarrow\ 12x = -84 \]
\[ \frac{12x}{12} = \frac{-84}{12} \ \Rightarrow\ x = -7 \]
\[ 12\cdot(-7) + 9 = -84 + 9 = -75 \checkmark \]

Trying values of x in 12x + 9 = −75

x	12x + 9	Equals -75?
-9	-99	no
-8	-87	no
-7	-75	yes
-6	-63	no
-5	-51	no

Questions

What is x in 12x + 9 = −75?

The solution of 12x + 9 = −75 is x = -7.

How do you solve 12x + 9 = −75?

Subtract 9 from both sides to get 12x = -84, then divide both sides by 12 to get x = -7.

How do I check the answer?

Replace x by -7: 12(-7) + 9 = -75, which is -75.

Solve 12x + 9 = −75

How to work it out

Trying values of x in 12x + 9 = −75

Questions

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