Solve 4x − 8 = 40

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

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

Explain it step by step in chat Make a short video of it

The lines y = 4x − 8 and y = 40 meet at x = 12. 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.
$4x - 8 = 40$
2
Add 8 to both sides:
$4x - 8 + 8 = 40 + 8 \ \Rightarrow\ 4x = 48$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{48}{4} \ \Rightarrow\ x = 12$
4
Check: put x = 12 back into the equation.
$4\cdot12 - 8 = 48 - 8 = 40 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 8 = 40\ \Rightarrow\ x = 12 \]
\[ 4x - 8 = 40 \]
\[ 4x - 8 + 8 = 40 + 8 \ \Rightarrow\ 4x = 48 \]
\[ \frac{4x}{4} = \frac{48}{4} \ \Rightarrow\ x = 12 \]
\[ 4\cdot12 - 8 = 48 - 8 = 40 \checkmark \]

Trying values of x in 4x − 8 = 40

x	4x − 8	Equals 40?
10	32	no
11	36	no
12	40	yes
13	44	no
14	48	no

Questions

What is x in 4x − 8 = 40?

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

How do you solve 4x − 8 = 40?

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

How do I check the answer?

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

Solve 4x − 8 = 40

How to work it out

Trying values of x in 4x − 8 = 40

Questions

Similar equations