Solve 9x − 12 = 15

The solution of 9x − 12 = 15 is x = 3.

9x - 12 = 15\ \Rightarrow\ x = 3

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The lines y = 9x − 12 and y = 15 meet at x = 3. 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.
$9x - 12 = 15$
2
Add 12 to both sides:
$9x - 12 + 12 = 15 + 12 \ \Rightarrow\ 9x = 27$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{27}{9} \ \Rightarrow\ x = 3$
4
Check: put x = 3 back into the equation.
$9\cdot3 - 12 = 27 - 12 = 15 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 12 = 15\ \Rightarrow\ x = 3 \]
\[ 9x - 12 = 15 \]
\[ 9x - 12 + 12 = 15 + 12 \ \Rightarrow\ 9x = 27 \]
\[ \frac{9x}{9} = \frac{27}{9} \ \Rightarrow\ x = 3 \]
\[ 9\cdot3 - 12 = 27 - 12 = 15 \checkmark \]

Trying values of x in 9x − 12 = 15

x	9x − 12	Equals 15?
1	-3	no
2	6	no
3	15	yes
4	24	no
5	33	no

Questions

What is x in 9x − 12 = 15?

The solution of 9x − 12 = 15 is x = 3.

How do you solve 9x − 12 = 15?

Add 12 to both sides to get 9x = 27, then divide both sides by 9 to get x = 3.

How do I check the answer?

Replace x by 3: 9(3) − 12 = 15, which is 15.

Solve 9x − 12 = 15

How to work it out

Trying values of x in 9x − 12 = 15

Questions

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