Solve 9x − 15 = 39

The solution of 9x − 15 = 39 is x = 6.

9x - 15 = 39\ \Rightarrow\ x = 6

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The lines y = 9x − 15 and y = 39 meet at x = 6. 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.
$9x - 15 = 39$
2
Add 15 to both sides:
$9x - 15 + 15 = 39 + 15 \ \Rightarrow\ 9x = 54$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{54}{9} \ \Rightarrow\ x = 6$
4
Check: put x = 6 back into the equation.
$9\cdot6 - 15 = 54 - 15 = 39 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 15 = 39\ \Rightarrow\ x = 6 \]
\[ 9x - 15 = 39 \]
\[ 9x - 15 + 15 = 39 + 15 \ \Rightarrow\ 9x = 54 \]
\[ \frac{9x}{9} = \frac{54}{9} \ \Rightarrow\ x = 6 \]
\[ 9\cdot6 - 15 = 54 - 15 = 39 \checkmark \]

Trying values of x in 9x − 15 = 39

x	9x − 15	Equals 39?
4	21	no
5	30	no
6	39	yes
7	48	no
8	57	no

Questions

What is x in 9x − 15 = 39?

The solution of 9x − 15 = 39 is x = 6.

How do you solve 9x − 15 = 39?

Add 15 to both sides to get 9x = 54, then divide both sides by 9 to get x = 6.

How do I check the answer?

Replace x by 6: 9(6) − 15 = 39, which is 39.

Solve 9x − 15 = 39

How to work it out

Trying values of x in 9x − 15 = 39

Questions

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