Solve 2x − 9 = 31

The solution of 2x − 9 = 31 is x = 20.

2x - 9 = 31\ \Rightarrow\ x = 20

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The lines y = 2x − 9 and y = 31 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.
$2x - 9 = 31$
2
Add 9 to both sides:
$2x - 9 + 9 = 31 + 9 \ \Rightarrow\ 2x = 40$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{40}{2} \ \Rightarrow\ x = 20$
4
Check: put x = 20 back into the equation.
$2\cdot20 - 9 = 40 - 9 = 31 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 9 = 31\ \Rightarrow\ x = 20 \]
\[ 2x - 9 = 31 \]
\[ 2x - 9 + 9 = 31 + 9 \ \Rightarrow\ 2x = 40 \]
\[ \frac{2x}{2} = \frac{40}{2} \ \Rightarrow\ x = 20 \]
\[ 2\cdot20 - 9 = 40 - 9 = 31 \checkmark \]

Trying values of x in 2x − 9 = 31

x	2x − 9	Equals 31?
18	27	no
19	29	no
20	31	yes
21	33	no
22	35	no

Questions

What is x in 2x − 9 = 31?

The solution of 2x − 9 = 31 is x = 20.

How do you solve 2x − 9 = 31?

Add 9 to both sides to get 2x = 40, then divide both sides by 2 to get x = 20.

How do I check the answer?

Replace x by 20: 2(20) − 9 = 31, which is 31.

Solve 2x − 9 = 31

How to work it out

Trying values of x in 2x − 9 = 31

Questions

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