Solve 3x − 6 = −21

The solution of 3x − 6 = −21 is x = -5.

3x - 6 = -21\ \Rightarrow\ x = -5

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The lines y = 3x − 6 and y = -21 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.
$3x - 6 = -21$
2
Add 6 to both sides:
$3x - 6 + 6 = -21 + 6 \ \Rightarrow\ 3x = -15$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{-15}{3} \ \Rightarrow\ x = -5$
4
Check: put x = -5 back into the equation.
$3\cdot(-5) - 6 = -15 - 6 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 6 = -21\ \Rightarrow\ x = -5 \]
\[ 3x - 6 = -21 \]
\[ 3x - 6 + 6 = -21 + 6 \ \Rightarrow\ 3x = -15 \]
\[ \frac{3x}{3} = \frac{-15}{3} \ \Rightarrow\ x = -5 \]
\[ 3\cdot(-5) - 6 = -15 - 6 = -21 \checkmark \]

Trying values of x in 3x − 6 = −21

x	3x − 6	Equals -21?
-7	-27	no
-6	-24	no
-5	-21	yes
-4	-18	no
-3	-15	no

Questions

What is x in 3x − 6 = −21?

The solution of 3x − 6 = −21 is x = -5.

How do you solve 3x − 6 = −21?

Add 6 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) − 6 = -21, which is -21.

Solve 3x − 6 = −21

How to work it out

Trying values of x in 3x − 6 = −21

Questions

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