Solve 12x + 15 = −105

The solution of 12x + 15 = −105 is x = -10.

12x + 15 = -105\ \Rightarrow\ x = -10

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The lines y = 12x + 15 and y = -105 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 addition, then the multiplication.
$12x + 15 = -105$
2
Subtract 15 from both sides:
$12x + 15 - 15 = -105 - 15 \ \Rightarrow\ 12x = -120$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-120}{12} \ \Rightarrow\ x = -10$
4
Check: put x = -10 back into the equation.
$12\cdot(-10) + 15 = -120 + 15 = -105 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 15 = -105\ \Rightarrow\ x = -10 \]
\[ 12x + 15 = -105 \]
\[ 12x + 15 - 15 = -105 - 15 \ \Rightarrow\ 12x = -120 \]
\[ \frac{12x}{12} = \frac{-120}{12} \ \Rightarrow\ x = -10 \]
\[ 12\cdot(-10) + 15 = -120 + 15 = -105 \checkmark \]

Trying values of x in 12x + 15 = −105

x	12x + 15	Equals -105?
-12	-129	no
-11	-117	no
-10	-105	yes
-9	-93	no
-8	-81	no

Questions

What is x in 12x + 15 = −105?

The solution of 12x + 15 = −105 is x = -10.

How do you solve 12x + 15 = −105?

Subtract 15 from 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) + 15 = -105, which is -105.

Solve 12x + 15 = −105

How to work it out

Trying values of x in 12x + 15 = −105

Questions

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