Solve 7x + 12 = 40

The solution of 7x + 12 = 40 is x = 4.

7x + 12 = 40\ \Rightarrow\ x = 4

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The lines y = 7x + 12 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 addition, then the multiplication.
$7x + 12 = 40$
2
Subtract 12 from both sides:
$7x + 12 - 12 = 40 - 12 \ \Rightarrow\ 7x = 28$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{28}{7} \ \Rightarrow\ x = 4$
4
Check: put x = 4 back into the equation.
$7\cdot4 + 12 = 28 + 12 = 40 \checkmark$

LaTeX source of the formulas on this page

\[ 7x + 12 = 40\ \Rightarrow\ x = 4 \]
\[ 7x + 12 = 40 \]
\[ 7x + 12 - 12 = 40 - 12 \ \Rightarrow\ 7x = 28 \]
\[ \frac{7x}{7} = \frac{28}{7} \ \Rightarrow\ x = 4 \]
\[ 7\cdot4 + 12 = 28 + 12 = 40 \checkmark \]

Trying values of x in 7x + 12 = 40

x	7x + 12	Equals 40?
2	26	no
3	33	no
4	40	yes
5	47	no
6	54	no

Questions

What is x in 7x + 12 = 40?

The solution of 7x + 12 = 40 is x = 4.

How do you solve 7x + 12 = 40?

Subtract 12 from both sides to get 7x = 28, then divide both sides by 7 to get x = 4.

How do I check the answer?

Replace x by 4: 7(4) + 12 = 40, which is 40.

Solve 7x + 12 = 40

How to work it out

Trying values of x in 7x + 12 = 40

Questions

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