Solve 9x − 8 = 109

The solution of 9x − 8 = 109 is x = 13.

9x - 8 = 109\ \Rightarrow\ x = 13

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The lines y = 9x − 8 and y = 109 meet at x = 13. 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.
$9x - 8 = 109$
2
Add 8 to both sides:
$9x - 8 + 8 = 109 + 8 \ \Rightarrow\ 9x = 117$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{117}{9} \ \Rightarrow\ x = 13$
4
Check: put x = 13 back into the equation.
$9\cdot13 - 8 = 117 - 8 = 109 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 8 = 109\ \Rightarrow\ x = 13 \]
\[ 9x - 8 = 109 \]
\[ 9x - 8 + 8 = 109 + 8 \ \Rightarrow\ 9x = 117 \]
\[ \frac{9x}{9} = \frac{117}{9} \ \Rightarrow\ x = 13 \]
\[ 9\cdot13 - 8 = 117 - 8 = 109 \checkmark \]

Trying values of x in 9x − 8 = 109

x	9x − 8	Equals 109?
11	91	no
12	100	no
13	109	yes
14	118	no
15	127	no

Questions

What is x in 9x − 8 = 109?

The solution of 9x − 8 = 109 is x = 13.

How do you solve 9x − 8 = 109?

Add 8 to both sides to get 9x = 117, then divide both sides by 9 to get x = 13.

How do I check the answer?

Replace x by 13: 9(13) − 8 = 109, which is 109.

Solve 9x − 8 = 109

How to work it out

Trying values of x in 9x − 8 = 109

Questions

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