Solve 5x − 9 = 51

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

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

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The lines y = 5x − 9 and y = 51 meet at x = 12. 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.
$5x - 9 = 51$
2
Add 9 to both sides:
$5x - 9 + 9 = 51 + 9 \ \Rightarrow\ 5x = 60$
3
Divide both sides by 5:
$\frac{5x}{5} = \frac{60}{5} \ \Rightarrow\ x = 12$
4
Check: put x = 12 back into the equation.
$5\cdot12 - 9 = 60 - 9 = 51 \checkmark$

LaTeX source of the formulas on this page

\[ 5x - 9 = 51\ \Rightarrow\ x = 12 \]
\[ 5x - 9 = 51 \]
\[ 5x - 9 + 9 = 51 + 9 \ \Rightarrow\ 5x = 60 \]
\[ \frac{5x}{5} = \frac{60}{5} \ \Rightarrow\ x = 12 \]
\[ 5\cdot12 - 9 = 60 - 9 = 51 \checkmark \]

Trying values of x in 5x − 9 = 51

x	5x − 9	Equals 51?
10	41	no
11	46	no
12	51	yes
13	56	no
14	61	no

Questions

What is x in 5x − 9 = 51?

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

How do you solve 5x − 9 = 51?

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

How do I check the answer?

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

Solve 5x − 9 = 51

How to work it out

Trying values of x in 5x − 9 = 51

Questions

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