Solve 3x − 12 = 30

The solution of 3x − 12 = 30 is x = 14.

3x - 12 = 30\ \Rightarrow\ x = 14

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The lines y = 3x − 12 and y = 30 meet at x = 14. 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.
$3x - 12 = 30$
2
Add 12 to both sides:
$3x - 12 + 12 = 30 + 12 \ \Rightarrow\ 3x = 42$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{42}{3} \ \Rightarrow\ x = 14$
4
Check: put x = 14 back into the equation.
$3\cdot14 - 12 = 42 - 12 = 30 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 12 = 30\ \Rightarrow\ x = 14 \]
\[ 3x - 12 = 30 \]
\[ 3x - 12 + 12 = 30 + 12 \ \Rightarrow\ 3x = 42 \]
\[ \frac{3x}{3} = \frac{42}{3} \ \Rightarrow\ x = 14 \]
\[ 3\cdot14 - 12 = 42 - 12 = 30 \checkmark \]

Trying values of x in 3x − 12 = 30

x	3x − 12	Equals 30?
12	24	no
13	27	no
14	30	yes
15	33	no
16	36	no

Questions

What is x in 3x − 12 = 30?

The solution of 3x − 12 = 30 is x = 14.

How do you solve 3x − 12 = 30?

Add 12 to both sides to get 3x = 42, then divide both sides by 3 to get x = 14.

How do I check the answer?

Replace x by 14: 3(14) − 12 = 30, which is 30.

Solve 3x − 12 = 30

How to work it out

Trying values of x in 3x − 12 = 30

Questions

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