Solve 9x − 15 = 165

The solution of 9x − 15 = 165 is x = 20.

9x - 15 = 165\ \Rightarrow\ x = 20

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The lines y = 9x − 15 and y = 165 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.
$9x - 15 = 165$
2
Add 15 to both sides:
$9x - 15 + 15 = 165 + 15 \ \Rightarrow\ 9x = 180$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{180}{9} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$9\cdot20 - 15 = 180 - 15 = 165 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 15 = 165\ \Rightarrow\ x = 20 \]
\[ 9x - 15 = 165 \]
\[ 9x - 15 + 15 = 165 + 15 \ \Rightarrow\ 9x = 180 \]
\[ \frac{9x}{9} = \frac{180}{9} \ \Rightarrow\ x = 20 \]
\[ 9\cdot20 - 15 = 180 - 15 = 165 \checkmark \]

Trying values of x in 9x − 15 = 165

x	9x − 15	Equals 165?
18	147	no
19	156	no
20	165	yes
21	174	no
22	183	no

Questions

What is x in 9x − 15 = 165?

The solution of 9x − 15 = 165 is x = 20.

How do you solve 9x − 15 = 165?

Add 15 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) − 15 = 165, which is 165.

Solve 9x − 15 = 165

How to work it out

Trying values of x in 9x − 15 = 165

Questions

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