Solve 7x − 14 = 21

The solution of 7x − 14 = 21 is x = 5.

7x - 14 = 21\ \Rightarrow\ x = 5

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The lines y = 7x − 14 and y = 21 meet at x = 5. 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.
$7x - 14 = 21$
2
Add 14 to both sides:
$7x - 14 + 14 = 21 + 14 \ \Rightarrow\ 7x = 35$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{35}{7} \ \Rightarrow\ x = 5$
4
Check: put x = 5 back into the equation.
$7\cdot5 - 14 = 35 - 14 = 21 \checkmark$

LaTeX source of the formulas on this page

\[ 7x - 14 = 21\ \Rightarrow\ x = 5 \]
\[ 7x - 14 = 21 \]
\[ 7x - 14 + 14 = 21 + 14 \ \Rightarrow\ 7x = 35 \]
\[ \frac{7x}{7} = \frac{35}{7} \ \Rightarrow\ x = 5 \]
\[ 7\cdot5 - 14 = 35 - 14 = 21 \checkmark \]

Trying values of x in 7x − 14 = 21

x	7x − 14	Equals 21?
3	7	no
4	14	no
5	21	yes
6	28	no
7	35	no

Questions

What is x in 7x − 14 = 21?

The solution of 7x − 14 = 21 is x = 5.

How do you solve 7x − 14 = 21?

Add 14 to both sides to get 7x = 35, then divide both sides by 7 to get x = 5.

How do I check the answer?

Replace x by 5: 7(5) − 14 = 21, which is 21.

Solve 7x − 14 = 21

How to work it out

Trying values of x in 7x − 14 = 21

Questions

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