Solve 2x − 7 = 21

The solution of 2x − 7 = 21 is x = 14.

2x - 7 = 21\ \Rightarrow\ x = 14

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The lines y = 2x − 7 and y = 21 meet at x = 14. 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.
$2x - 7 = 21$
2
Add 7 to both sides:
$2x - 7 + 7 = 21 + 7 \ \Rightarrow\ 2x = 28$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{28}{2} \ \Rightarrow\ x = 14$
4
Check: put x = 14 back into the equation.
$2\cdot14 - 7 = 28 - 7 = 21 \checkmark$

LaTeX source of the formulas on this page

\[ 2x - 7 = 21\ \Rightarrow\ x = 14 \]
\[ 2x - 7 = 21 \]
\[ 2x - 7 + 7 = 21 + 7 \ \Rightarrow\ 2x = 28 \]
\[ \frac{2x}{2} = \frac{28}{2} \ \Rightarrow\ x = 14 \]
\[ 2\cdot14 - 7 = 28 - 7 = 21 \checkmark \]

Trying values of x in 2x − 7 = 21

x	2x − 7	Equals 21?
12	17	no
13	19	no
14	21	yes
15	23	no
16	25	no

Questions

What is x in 2x − 7 = 21?

The solution of 2x − 7 = 21 is x = 14.

How do you solve 2x − 7 = 21?

Add 7 to both sides to get 2x = 28, then divide both sides by 2 to get x = 14.

How do I check the answer?

Replace x by 14: 2(14) − 7 = 21, which is 21.

Solve 2x − 7 = 21

How to work it out

Trying values of x in 2x − 7 = 21

Questions

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