Solve 6x − 9 = 15

The solution of 6x − 9 = 15 is x = 4.

6x - 9 = 15\ \Rightarrow\ x = 4

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The lines y = 6x − 9 and y = 15 meet at x = 4. 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.
$6x - 9 = 15$
2
Add 9 to both sides:
$6x - 9 + 9 = 15 + 9 \ \Rightarrow\ 6x = 24$
3
Divide both sides by 6:
$\frac{6x}{6} = \frac{24}{6} \ \Rightarrow\ x = 4$
4
Check: put x = 4 back into the equation.
$6\cdot4 - 9 = 24 - 9 = 15 \checkmark$

LaTeX source of the formulas on this page

\[ 6x - 9 = 15\ \Rightarrow\ x = 4 \]
\[ 6x - 9 = 15 \]
\[ 6x - 9 + 9 = 15 + 9 \ \Rightarrow\ 6x = 24 \]
\[ \frac{6x}{6} = \frac{24}{6} \ \Rightarrow\ x = 4 \]
\[ 6\cdot4 - 9 = 24 - 9 = 15 \checkmark \]

Trying values of x in 6x − 9 = 15

x	6x − 9	Equals 15?
2	3	no
3	9	no
4	15	yes
5	21	no
6	27	no

Questions

What is x in 6x − 9 = 15?

The solution of 6x − 9 = 15 is x = 4.

How do you solve 6x − 9 = 15?

Add 9 to both sides to get 6x = 24, then divide both sides by 6 to get x = 4.

How do I check the answer?

Replace x by 4: 6(4) − 9 = 15, which is 15.

Solve 6x − 9 = 15

How to work it out

Trying values of x in 6x − 9 = 15

Questions

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