Solve 8x − 9 = 39

The solution of 8x − 9 = 39 is x = 6.

8x - 9 = 39\ \Rightarrow\ x = 6

Explain it step by step in chat Make a short video of it

The lines y = 8x − 9 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.
$8x - 9 = 39$
2
Add 9 to both sides:
$8x - 9 + 9 = 39 + 9 \ \Rightarrow\ 8x = 48$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{48}{8} \ \Rightarrow\ x = 6$
4
Check: put x = 6 back into the equation.
$8\cdot6 - 9 = 48 - 9 = 39 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 9 = 39\ \Rightarrow\ x = 6 \]
\[ 8x - 9 = 39 \]
\[ 8x - 9 + 9 = 39 + 9 \ \Rightarrow\ 8x = 48 \]
\[ \frac{8x}{8} = \frac{48}{8} \ \Rightarrow\ x = 6 \]
\[ 8\cdot6 - 9 = 48 - 9 = 39 \checkmark \]

Trying values of x in 8x − 9 = 39

x	8x − 9	Equals 39?
4	23	no
5	31	no
6	39	yes
7	47	no
8	55	no

Questions

What is x in 8x − 9 = 39?

The solution of 8x − 9 = 39 is x = 6.

How do you solve 8x − 9 = 39?

Add 9 to both sides to get 8x = 48, then divide both sides by 8 to get x = 6.

How do I check the answer?

Replace x by 6: 8(6) − 9 = 39, which is 39.

Solve 8x − 9 = 39

How to work it out

Trying values of x in 8x − 9 = 39

Questions

Similar equations