Solve 2x + 8 = 40

The solution of 2x + 8 = 40 is x = 16.

2x + 8 = 40\ \Rightarrow\ x = 16

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The lines y = 2x + 8 and y = 40 meet at x = 16. 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 addition, then the multiplication.
$2x + 8 = 40$
2
Subtract 8 from both sides:
$2x + 8 - 8 = 40 - 8 \ \Rightarrow\ 2x = 32$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{32}{2} \ \Rightarrow\ x = 16$
4
Check: put x = 16 back into the equation.
$2\cdot16 + 8 = 32 + 8 = 40 \checkmark$

LaTeX source of the formulas on this page

\[ 2x + 8 = 40\ \Rightarrow\ x = 16 \]
\[ 2x + 8 = 40 \]
\[ 2x + 8 - 8 = 40 - 8 \ \Rightarrow\ 2x = 32 \]
\[ \frac{2x}{2} = \frac{32}{2} \ \Rightarrow\ x = 16 \]
\[ 2\cdot16 + 8 = 32 + 8 = 40 \checkmark \]

Trying values of x in 2x + 8 = 40

x	2x + 8	Equals 40?
14	36	no
15	38	no
16	40	yes
17	42	no
18	44	no

Questions

What is x in 2x + 8 = 40?

The solution of 2x + 8 = 40 is x = 16.

How do you solve 2x + 8 = 40?

Subtract 8 from both sides to get 2x = 32, then divide both sides by 2 to get x = 16.

How do I check the answer?

Replace x by 16: 2(16) + 8 = 40, which is 40.

Solve 2x + 8 = 40

How to work it out

Trying values of x in 2x + 8 = 40

Questions

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