Solve 2x + 9 = 31

The solution of 2x + 9 = 31 is x = 11.

2x + 9 = 31\ \Rightarrow\ x = 11

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The lines y = 2x + 9 and y = 31 meet at x = 11. 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 addition, then the multiplication.
$2x + 9 = 31$
2
Subtract 9 from both sides:
$2x + 9 - 9 = 31 - 9 \ \Rightarrow\ 2x = 22$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{22}{2} \ \Rightarrow\ x = 11$
4
Check: put x = 11 back into the equation.
$2\cdot11 + 9 = 22 + 9 = 31 \checkmark$

LaTeX source of the formulas on this page

\[ 2x + 9 = 31\ \Rightarrow\ x = 11 \]
\[ 2x + 9 = 31 \]
\[ 2x + 9 - 9 = 31 - 9 \ \Rightarrow\ 2x = 22 \]
\[ \frac{2x}{2} = \frac{22}{2} \ \Rightarrow\ x = 11 \]
\[ 2\cdot11 + 9 = 22 + 9 = 31 \checkmark \]

Trying values of x in 2x + 9 = 31

x	2x + 9	Equals 31?
9	27	no
10	29	no
11	31	yes
12	33	no
13	35	no

Questions

What is x in 2x + 9 = 31?

The solution of 2x + 9 = 31 is x = 11.

How do you solve 2x + 9 = 31?

Subtract 9 from both sides to get 2x = 22, then divide both sides by 2 to get x = 11.

How do I check the answer?

Replace x by 11: 2(11) + 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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