Solve 2x + 4 = 40

The solution of 2x + 4 = 40 is x = 18.

2x + 4 = 40\ \Rightarrow\ x = 18

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The lines y = 2x + 4 and y = 40 meet at x = 18. 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.
$2x + 4 = 40$
2
Subtract 4 from both sides:
$2x + 4 - 4 = 40 - 4 \ \Rightarrow\ 2x = 36$
3
Divide both sides by 2:
$\frac{2x}{2} = \frac{36}{2} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$2\cdot18 + 4 = 36 + 4 = 40 \checkmark$

LaTeX source of the formulas on this page

\[ 2x + 4 = 40\ \Rightarrow\ x = 18 \]
\[ 2x + 4 = 40 \]
\[ 2x + 4 - 4 = 40 - 4 \ \Rightarrow\ 2x = 36 \]
\[ \frac{2x}{2} = \frac{36}{2} \ \Rightarrow\ x = 18 \]
\[ 2\cdot18 + 4 = 36 + 4 = 40 \checkmark \]

Trying values of x in 2x + 4 = 40

x	2x + 4	Equals 40?
16	36	no
17	38	no
18	40	yes
19	42	no
20	44	no

Questions

What is x in 2x + 4 = 40?

The solution of 2x + 4 = 40 is x = 18.

How do you solve 2x + 4 = 40?

Subtract 4 from both sides to get 2x = 36, then divide both sides by 2 to get x = 18.

How do I check the answer?

Replace x by 18: 2(18) + 4 = 40, which is 40.

Solve 2x + 4 = 40

How to work it out

Trying values of x in 2x + 4 = 40

Questions

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