Solve 12x + 15 = −45

The solution of 12x + 15 = −45 is x = -5.

12x + 15 = -45\ \Rightarrow\ x = -5

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The lines y = 12x + 15 and y = -45 meet at x = -5. 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.
$12x + 15 = -45$
2
Subtract 15 from both sides:
$12x + 15 - 15 = -45 - 15 \ \Rightarrow\ 12x = -60$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-60}{12} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$12\cdot(-5) + 15 = -60 + 15 = -45 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 15 = -45\ \Rightarrow\ x = -5 \]
\[ 12x + 15 = -45 \]
\[ 12x + 15 - 15 = -45 - 15 \ \Rightarrow\ 12x = -60 \]
\[ \frac{12x}{12} = \frac{-60}{12} \ \Rightarrow\ x = -5 \]
\[ 12\cdot(-5) + 15 = -60 + 15 = -45 \checkmark \]

Trying values of x in 12x + 15 = −45

x	12x + 15	Equals -45?
-7	-69	no
-6	-57	no
-5	-45	yes
-4	-33	no
-3	-21	no

Questions

What is x in 12x + 15 = −45?

The solution of 12x + 15 = −45 is x = -5.

How do you solve 12x + 15 = −45?

Subtract 15 from both sides to get 12x = -60, then divide both sides by 12 to get x = -5.

How do I check the answer?

Replace x by -5: 12(-5) + 15 = -45, which is -45.

Solve 12x + 15 = −45

How to work it out

Trying values of x in 12x + 15 = −45

Questions

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