Solve 3x + 15 = −6

The solution of 3x + 15 = −6 is x = -7.

3x + 15 = -6\ \Rightarrow\ x = -7

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The lines y = 3x + 15 and y = -6 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.
$3x + 15 = -6$
2
Subtract 15 from both sides:
$3x + 15 - 15 = -6 - 15 \ \Rightarrow\ 3x = -21$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{-21}{3} \ \Rightarrow\ x = -7$
4
Check: put x = -7 back into the equation.
$3\cdot(-7) + 15 = -21 + 15 = -6 \checkmark$

LaTeX source of the formulas on this page

\[ 3x + 15 = -6\ \Rightarrow\ x = -7 \]
\[ 3x + 15 = -6 \]
\[ 3x + 15 - 15 = -6 - 15 \ \Rightarrow\ 3x = -21 \]
\[ \frac{3x}{3} = \frac{-21}{3} \ \Rightarrow\ x = -7 \]
\[ 3\cdot(-7) + 15 = -21 + 15 = -6 \checkmark \]

Trying values of x in 3x + 15 = −6

x	3x + 15	Equals -6?
-9	-12	no
-8	-9	no
-7	-6	yes
-6	-3	no
-5	0	no

Questions

What is x in 3x + 15 = −6?

The solution of 3x + 15 = −6 is x = -7.

How do you solve 3x + 15 = −6?

Subtract 15 from both sides to get 3x = -21, then divide both sides by 3 to get x = -7.

How do I check the answer?

Replace x by -7: 3(-7) + 15 = -6, which is -6.

Solve 3x + 15 = −6

How to work it out

Trying values of x in 3x + 15 = −6

Questions

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