Solve 12x − 9 = 51

The solution of 12x − 9 = 51 is x = 5.

12x - 9 = 51\ \Rightarrow\ x = 5

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The lines y = 12x − 9 and y = 51 meet at x = 5. 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.
$12x - 9 = 51$
2
Add 9 to both sides:
$12x - 9 + 9 = 51 + 9 \ \Rightarrow\ 12x = 60$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{60}{12} \ \Rightarrow\ x = 5$
4
Check: put x = 5 back into the equation.
$12\cdot5 - 9 = 60 - 9 = 51 \checkmark$

LaTeX source of the formulas on this page

\[ 12x - 9 = 51\ \Rightarrow\ x = 5 \]
\[ 12x - 9 = 51 \]
\[ 12x - 9 + 9 = 51 + 9 \ \Rightarrow\ 12x = 60 \]
\[ \frac{12x}{12} = \frac{60}{12} \ \Rightarrow\ x = 5 \]
\[ 12\cdot5 - 9 = 60 - 9 = 51 \checkmark \]

Trying values of x in 12x − 9 = 51

x	12x − 9	Equals 51?
3	27	no
4	39	no
5	51	yes
6	63	no
7	75	no

Questions

What is x in 12x − 9 = 51?

The solution of 12x − 9 = 51 is x = 5.

How do you solve 12x − 9 = 51?

Add 9 to both sides to get 12x = 60, then divide both sides by 12 to get x = 5.

How do I check the answer?

Replace x by 5: 12(5) − 9 = 51, which is 51.

Solve 12x − 9 = 51

How to work it out

Trying values of x in 12x − 9 = 51

Questions

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