Solve 3x − 3 = −21

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

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

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The lines y = 3x − 3 and y = -21 meet at x = -6. 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.
$3x - 3 = -21$
2
Add 3 to both sides:
$3x - 3 + 3 = -21 + 3 \ \Rightarrow\ 3x = -18$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{-18}{3} \ \Rightarrow\ x = -6$
4
Check: put x = -6 back into the equation.
$3\cdot(-6) - 3 = -18 - 3 = -21 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 3 = -21\ \Rightarrow\ x = -6 \]
\[ 3x - 3 = -21 \]
\[ 3x - 3 + 3 = -21 + 3 \ \Rightarrow\ 3x = -18 \]
\[ \frac{3x}{3} = \frac{-18}{3} \ \Rightarrow\ x = -6 \]
\[ 3\cdot(-6) - 3 = -18 - 3 = -21 \checkmark \]

Trying values of x in 3x − 3 = −21

x	3x − 3	Equals -21?
-8	-27	no
-7	-24	no
-6	-21	yes
-5	-18	no
-4	-15	no

Questions

What is x in 3x − 3 = −21?

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

How do you solve 3x − 3 = −21?

Add 3 to both sides to get 3x = -18, then divide both sides by 3 to get x = -6.

How do I check the answer?

Replace x by -6: 3(-6) − 3 = -21, which is -21.

Solve 3x − 3 = −21

How to work it out

Trying values of x in 3x − 3 = −21

Questions

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