Solve 9x − 9 = 171

The solution of 9x − 9 = 171 is x = 20.

9x - 9 = 171\ \Rightarrow\ x = 20

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The lines y = 9x − 9 and y = 171 meet at x = 20. 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.
$9x - 9 = 171$
2
Add 9 to both sides:
$9x - 9 + 9 = 171 + 9 \ \Rightarrow\ 9x = 180$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{180}{9} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$9\cdot20 - 9 = 180 - 9 = 171 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 9 = 171\ \Rightarrow\ x = 20 \]
\[ 9x - 9 = 171 \]
\[ 9x - 9 + 9 = 171 + 9 \ \Rightarrow\ 9x = 180 \]
\[ \frac{9x}{9} = \frac{180}{9} \ \Rightarrow\ x = 20 \]
\[ 9\cdot20 - 9 = 180 - 9 = 171 \checkmark \]

Trying values of x in 9x − 9 = 171

x	9x − 9	Equals 171?
18	153	no
19	162	no
20	171	yes
21	180	no
22	189	no

Questions

What is x in 9x − 9 = 171?

The solution of 9x − 9 = 171 is x = 20.

How do you solve 9x − 9 = 171?

Add 9 to both sides to get 9x = 180, then divide both sides by 9 to get x = 20.

How do I check the answer?

Replace x by 20: 9(20) − 9 = 171, which is 171.

Solve 9x − 9 = 171

How to work it out

Trying values of x in 9x − 9 = 171

Questions

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