Solve 4x − 8 = 12

The solution of 4x − 8 = 12 is x = 5.

4x - 8 = 12\ \Rightarrow\ x = 5

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The lines y = 4x − 8 and y = 12 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.
$4x - 8 = 12$
2
Add 8 to both sides:
$4x - 8 + 8 = 12 + 8 \ \Rightarrow\ 4x = 20$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{20}{4} \ \Rightarrow\ x = 5$
4
Check: put x = 5 back into the equation.
$4\cdot5 - 8 = 20 - 8 = 12 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 8 = 12\ \Rightarrow\ x = 5 \]
\[ 4x - 8 = 12 \]
\[ 4x - 8 + 8 = 12 + 8 \ \Rightarrow\ 4x = 20 \]
\[ \frac{4x}{4} = \frac{20}{4} \ \Rightarrow\ x = 5 \]
\[ 4\cdot5 - 8 = 20 - 8 = 12 \checkmark \]

Trying values of x in 4x − 8 = 12

x	4x − 8	Equals 12?
3	4	no
4	8	no
5	12	yes
6	16	no
7	20	no

Questions

What is x in 4x − 8 = 12?

The solution of 4x − 8 = 12 is x = 5.

How do you solve 4x − 8 = 12?

Add 8 to both sides to get 4x = 20, then divide both sides by 4 to get x = 5.

How do I check the answer?

Replace x by 5: 4(5) − 8 = 12, which is 12.

Solve 4x − 8 = 12

How to work it out

Trying values of x in 4x − 8 = 12

Questions

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