Solve 3x − 15 = −30

The solution of 3x − 15 = −30 is x = -5.

3x - 15 = -30\ \Rightarrow\ x = -5

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The lines y = 3x − 15 and y = -30 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 subtraction, then the multiplication.
$3x - 15 = -30$
2
Add 15 to both sides:
$3x - 15 + 15 = -30 + 15 \ \Rightarrow\ 3x = -15$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{-15}{3} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$3\cdot(-5) - 15 = -15 - 15 = -30 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 15 = -30\ \Rightarrow\ x = -5 \]
\[ 3x - 15 = -30 \]
\[ 3x - 15 + 15 = -30 + 15 \ \Rightarrow\ 3x = -15 \]
\[ \frac{3x}{3} = \frac{-15}{3} \ \Rightarrow\ x = -5 \]
\[ 3\cdot(-5) - 15 = -15 - 15 = -30 \checkmark \]

Trying values of x in 3x − 15 = −30

x	3x − 15	Equals -30?
-7	-36	no
-6	-33	no
-5	-30	yes
-4	-27	no
-3	-24	no

Questions

What is x in 3x − 15 = −30?

The solution of 3x − 15 = −30 is x = -5.

How do you solve 3x − 15 = −30?

Add 15 to both sides to get 3x = -15, then divide both sides by 3 to get x = -5.

How do I check the answer?

Replace x by -5: 3(-5) − 15 = -30, which is -30.

Solve 3x − 15 = −30

How to work it out

Trying values of x in 3x − 15 = −30

Questions

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