Solve 2x − 13 = 21

The solution of 2x − 13 = 21 is x = 17.

2x - 13 = 21\ \Rightarrow\ x = 17

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The lines y = 2x − 13 and y = 21 meet at x = 17. 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.
$2x - 13 = 21$
2
Add 13 to both sides:
$2x - 13 + 13 = 21 + 13 \ \Rightarrow\ 2x = 34$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{34}{2} \ \Rightarrow\ x = 17$
4
Check: put x = 17 back into the equation.
$2\cdot17 - 13 = 34 - 13 = 21 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 13 = 21\ \Rightarrow\ x = 17 \]
\[ 2x - 13 = 21 \]
\[ 2x - 13 + 13 = 21 + 13 \ \Rightarrow\ 2x = 34 \]
\[ \frac{2x}{2} = \frac{34}{2} \ \Rightarrow\ x = 17 \]
\[ 2\cdot17 - 13 = 34 - 13 = 21 \checkmark \]

Trying values of x in 2x − 13 = 21

x	2x − 13	Equals 21?
15	17	no
16	19	no
17	21	yes
18	23	no
19	25	no

Questions

What is x in 2x − 13 = 21?

The solution of 2x − 13 = 21 is x = 17.

How do you solve 2x − 13 = 21?

Add 13 to both sides to get 2x = 34, then divide both sides by 2 to get x = 17.

How do I check the answer?

Replace x by 17: 2(17) − 13 = 21, which is 21.

Solve 2x − 13 = 21

How to work it out

Trying values of x in 2x − 13 = 21

Questions

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