Solve 8x − 13 = 123

The solution of 8x − 13 = 123 is x = 17.

8x - 13 = 123\ \Rightarrow\ x = 17

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The lines y = 8x − 13 and y = 123 meet at x = 17. 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.
$8x - 13 = 123$
2
Add 13 to both sides:
$8x - 13 + 13 = 123 + 13 \ \Rightarrow\ 8x = 136$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{136}{8} \ \Rightarrow\ x = 17$
4
Check: put x = 17 back into the equation.
$8\cdot17 - 13 = 136 - 13 = 123 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 13 = 123\ \Rightarrow\ x = 17 \]
\[ 8x - 13 = 123 \]
\[ 8x - 13 + 13 = 123 + 13 \ \Rightarrow\ 8x = 136 \]
\[ \frac{8x}{8} = \frac{136}{8} \ \Rightarrow\ x = 17 \]
\[ 8\cdot17 - 13 = 136 - 13 = 123 \checkmark \]

Trying values of x in 8x − 13 = 123

x	8x − 13	Equals 123?
15	107	no
16	115	no
17	123	yes
18	131	no
19	139	no

Questions

What is x in 8x − 13 = 123?

The solution of 8x − 13 = 123 is x = 17.

How do you solve 8x − 13 = 123?

Add 13 to both sides to get 8x = 136, then divide both sides by 8 to get x = 17.

How do I check the answer?

Replace x by 17: 8(17) − 13 = 123, which is 123.

Solve 8x − 13 = 123

How to work it out

Trying values of x in 8x − 13 = 123

Questions

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