Solve 3x − 6 = 39

The solution of 3x − 6 = 39 is x = 15.

3x - 6 = 39\ \Rightarrow\ x = 15

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The lines y = 3x − 6 and y = 39 meet at x = 15. 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.
$3x - 6 = 39$
2
Add 6 to both sides:
$3x - 6 + 6 = 39 + 6 \ \Rightarrow\ 3x = 45$
3
Divide both sides by 3:
$\frac{3x}{3} = \frac{45}{3} \ \Rightarrow\ x = 15$
4
Check: put x = 15 back into the equation.
$3\cdot15 - 6 = 45 - 6 = 39 \checkmark$

LaTeX source of the formulas on this page

\[ 3x - 6 = 39\ \Rightarrow\ x = 15 \]
\[ 3x - 6 = 39 \]
\[ 3x - 6 + 6 = 39 + 6 \ \Rightarrow\ 3x = 45 \]
\[ \frac{3x}{3} = \frac{45}{3} \ \Rightarrow\ x = 15 \]
\[ 3\cdot15 - 6 = 45 - 6 = 39 \checkmark \]

Trying values of x in 3x − 6 = 39

x	3x − 6	Equals 39?
13	33	no
14	36	no
15	39	yes
16	42	no
17	45	no

Questions

What is x in 3x − 6 = 39?

The solution of 3x − 6 = 39 is x = 15.

How do you solve 3x − 6 = 39?

Add 6 to both sides to get 3x = 45, then divide both sides by 3 to get x = 15.

How do I check the answer?

Replace x by 15: 3(15) − 6 = 39, which is 39.

Solve 3x − 6 = 39

How to work it out

Trying values of x in 3x − 6 = 39

Questions

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