Solve 2x − 9 = 15

The solution of 2x − 9 = 15 is x = 12.

2x - 9 = 15\ \Rightarrow\ x = 12

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The lines y = 2x − 9 and y = 15 meet at x = 12. 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.
$2x - 9 = 15$
2
Add 9 to both sides:
$2x - 9 + 9 = 15 + 9 \ \Rightarrow\ 2x = 24$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{24}{2} \ \Rightarrow\ x = 12$
4
Check: put x = 12 back into the equation.
$2\cdot12 - 9 = 24 - 9 = 15 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 9 = 15\ \Rightarrow\ x = 12 \]
\[ 2x - 9 = 15 \]
\[ 2x - 9 + 9 = 15 + 9 \ \Rightarrow\ 2x = 24 \]
\[ \frac{2x}{2} = \frac{24}{2} \ \Rightarrow\ x = 12 \]
\[ 2\cdot12 - 9 = 24 - 9 = 15 \checkmark \]

Trying values of x in 2x − 9 = 15

x	2x − 9	Equals 15?
10	11	no
11	13	no
12	15	yes
13	17	no
14	19	no

Questions

What is x in 2x − 9 = 15?

The solution of 2x − 9 = 15 is x = 12.

How do you solve 2x − 9 = 15?

Add 9 to both sides to get 2x = 24, then divide both sides by 2 to get x = 12.

How do I check the answer?

Replace x by 12: 2(12) − 9 = 15, which is 15.

Solve 2x − 9 = 15

How to work it out

Trying values of x in 2x − 9 = 15

Questions

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