Solve 4x − 15 = 9

The solution of 4x − 15 = 9 is x = 6.

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

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The lines y = 4x − 15 and y = 9 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.
$4x - 15 = 9$
2
Add 15 to both sides:
$4x - 15 + 15 = 9 + 15 \ \Rightarrow\ 4x = 24$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{24}{4} \ \Rightarrow\ x = 6$
4
Check: put x = 6 back into the equation.
$4\cdot6 - 15 = 24 - 15 = 9 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 15 = 9\ \Rightarrow\ x = 6 \]
\[ 4x - 15 = 9 \]
\[ 4x - 15 + 15 = 9 + 15 \ \Rightarrow\ 4x = 24 \]
\[ \frac{4x}{4} = \frac{24}{4} \ \Rightarrow\ x = 6 \]
\[ 4\cdot6 - 15 = 24 - 15 = 9 \checkmark \]

Trying values of x in 4x − 15 = 9

x	4x − 15	Equals 9?
4	1	no
5	5	no
6	9	yes
7	13	no
8	17	no

Questions

What is x in 4x − 15 = 9?

The solution of 4x − 15 = 9 is x = 6.

How do you solve 4x − 15 = 9?

Add 15 to both sides to get 4x = 24, then divide both sides by 4 to get x = 6.

How do I check the answer?

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

Solve 4x − 15 = 9

How to work it out

Trying values of x in 4x − 15 = 9

Questions

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