Solve 3x − 8 = 13

The solution of 3x − 8 = 13 is x = 7.

3x - 8 = 13\ \Rightarrow\ x = 7

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The lines y = 3x − 8 and y = 13 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 subtraction, then the multiplication.
$3x - 8 = 13$
2
Add 8 to both sides:
$3x - 8 + 8 = 13 + 8 \ \Rightarrow\ 3x = 21$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{21}{3} \ \Rightarrow\ x = 7$
4
Check: put x = 7 back into the equation.
$3\cdot7 - 8 = 21 - 8 = 13 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 8 = 13\ \Rightarrow\ x = 7 \]
\[ 3x - 8 = 13 \]
\[ 3x - 8 + 8 = 13 + 8 \ \Rightarrow\ 3x = 21 \]
\[ \frac{3x}{3} = \frac{21}{3} \ \Rightarrow\ x = 7 \]
\[ 3\cdot7 - 8 = 21 - 8 = 13 \checkmark \]

Trying values of x in 3x − 8 = 13

x	3x − 8	Equals 13?
5	7	no
6	10	no
7	13	yes
8	16	no
9	19	no

Questions

What is x in 3x − 8 = 13?

The solution of 3x − 8 = 13 is x = 7.

How do you solve 3x − 8 = 13?

Add 8 to 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) − 8 = 13, which is 13.

Solve 3x − 8 = 13

How to work it out

Trying values of x in 3x − 8 = 13

Questions

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