Solve 12x − 8 = 40

The solution of 12x − 8 = 40 is x = 4.

12x - 8 = 40\ \Rightarrow\ x = 4

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The lines y = 12x − 8 and y = 40 meet at x = 4. 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.
$12x - 8 = 40$
2
Add 8 to both sides:
$12x - 8 + 8 = 40 + 8 \ \Rightarrow\ 12x = 48$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{48}{12} \ \Rightarrow\ x = 4$
4
Check: put x = 4 back into the equation.
$12\cdot4 - 8 = 48 - 8 = 40 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 8 = 40\ \Rightarrow\ x = 4 \]
\[ 12x - 8 = 40 \]
\[ 12x - 8 + 8 = 40 + 8 \ \Rightarrow\ 12x = 48 \]
\[ \frac{12x}{12} = \frac{48}{12} \ \Rightarrow\ x = 4 \]
\[ 12\cdot4 - 8 = 48 - 8 = 40 \checkmark \]

Trying values of x in 12x − 8 = 40

x	12x − 8	Equals 40?
2	16	no
3	28	no
4	40	yes
5	52	no
6	64	no

Questions

What is x in 12x − 8 = 40?

The solution of 12x − 8 = 40 is x = 4.

How do you solve 12x − 8 = 40?

Add 8 to both sides to get 12x = 48, then divide both sides by 12 to get x = 4.

How do I check the answer?

Replace x by 4: 12(4) − 8 = 40, which is 40.

Solve 12x − 8 = 40

How to work it out

Trying values of x in 12x − 8 = 40

Questions

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