Solve 7x + 12 = 138

The solution of 7x + 12 = 138 is x = 18.

7x + 12 = 138\ \Rightarrow\ x = 18

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The lines y = 7x + 12 and y = 138 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.
$7x + 12 = 138$
2
Subtract 12 from both sides:
$7x + 12 - 12 = 138 - 12 \ \Rightarrow\ 7x = 126$
3
Divide both sides by 7:
$\frac{7x}{7} = \frac{126}{7} \ \Rightarrow\ x = 18$
4
Check: put x = 18 back into the equation.
$7\cdot18 + 12 = 126 + 12 = 138 \checkmark$

LaTeX source of the formulas on this page

\[ 7x + 12 = 138\ \Rightarrow\ x = 18 \]
\[ 7x + 12 = 138 \]
\[ 7x + 12 - 12 = 138 - 12 \ \Rightarrow\ 7x = 126 \]
\[ \frac{7x}{7} = \frac{126}{7} \ \Rightarrow\ x = 18 \]
\[ 7\cdot18 + 12 = 126 + 12 = 138 \checkmark \]

Trying values of x in 7x + 12 = 138

x	7x + 12	Equals 138?
16	124	no
17	131	no
18	138	yes
19	145	no
20	152	no

Questions

What is x in 7x + 12 = 138?

The solution of 7x + 12 = 138 is x = 18.

How do you solve 7x + 12 = 138?

Subtract 12 from both sides to get 7x = 126, then divide both sides by 7 to get x = 18.

How do I check the answer?

Replace x by 18: 7(18) + 12 = 138, which is 138.

Solve 7x + 12 = 138

How to work it out

Trying values of x in 7x + 12 = 138

Questions

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