Solve 12x − 9 = 99

The solution of 12x − 9 = 99 is x = 9.

12x - 9 = 99\ \Rightarrow\ x = 9

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The lines y = 12x − 9 and y = 99 meet at x = 9. 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.
$12x - 9 = 99$
2
Add 9 to both sides:
$12x - 9 + 9 = 99 + 9 \ \Rightarrow\ 12x = 108$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{108}{12} \ \Rightarrow\ x = 9$
4
Check: put x = 9 back into the equation.
$12\cdot9 - 9 = 108 - 9 = 99 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 9 = 99\ \Rightarrow\ x = 9 \]
\[ 12x - 9 = 99 \]
\[ 12x - 9 + 9 = 99 + 9 \ \Rightarrow\ 12x = 108 \]
\[ \frac{12x}{12} = \frac{108}{12} \ \Rightarrow\ x = 9 \]
\[ 12\cdot9 - 9 = 108 - 9 = 99 \checkmark \]

Trying values of x in 12x − 9 = 99

x	12x − 9	Equals 99?
7	75	no
8	87	no
9	99	yes
10	111	no
11	123	no

Questions

What is x in 12x − 9 = 99?

The solution of 12x − 9 = 99 is x = 9.

How do you solve 12x − 9 = 99?

Add 9 to both sides to get 12x = 108, then divide both sides by 12 to get x = 9.

How do I check the answer?

Replace x by 9: 12(9) − 9 = 99, which is 99.

Solve 12x − 9 = 99

How to work it out

Trying values of x in 12x − 9 = 99

Questions

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