Solve 8x − 9 = 111

The solution of 8x − 9 = 111 is x = 15.

8x - 9 = 111\ \Rightarrow\ x = 15

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The lines y = 8x − 9 and y = 111 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.
$8x - 9 = 111$
2
Add 9 to both sides:
$8x - 9 + 9 = 111 + 9 \ \Rightarrow\ 8x = 120$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{120}{8} \ \Rightarrow\ x = 15$
4
Check: put x = 15 back into the equation.
$8\cdot15 - 9 = 120 - 9 = 111 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 9 = 111\ \Rightarrow\ x = 15 \]
\[ 8x - 9 = 111 \]
\[ 8x - 9 + 9 = 111 + 9 \ \Rightarrow\ 8x = 120 \]
\[ \frac{8x}{8} = \frac{120}{8} \ \Rightarrow\ x = 15 \]
\[ 8\cdot15 - 9 = 120 - 9 = 111 \checkmark \]

Trying values of x in 8x − 9 = 111

x	8x − 9	Equals 111?
13	95	no
14	103	no
15	111	yes
16	119	no
17	127	no

Questions

What is x in 8x − 9 = 111?

The solution of 8x − 9 = 111 is x = 15.

How do you solve 8x − 9 = 111?

Add 9 to both sides to get 8x = 120, then divide both sides by 8 to get x = 15.

How do I check the answer?

Replace x by 15: 8(15) − 9 = 111, which is 111.

Solve 8x − 9 = 111

How to work it out

Trying values of x in 8x − 9 = 111

Questions

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