Solve 10x − 9 = 111

The solution of 10x − 9 = 111 is x = 12.

10x - 9 = 111\ \Rightarrow\ x = 12

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The lines y = 10x − 9 and y = 111 meet at x = 12. 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.
$10x - 9 = 111$
2
Add 9 to both sides:
$10x - 9 + 9 = 111 + 9 \ \Rightarrow\ 10x = 120$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{120}{10} \ \Rightarrow\ x = 12$
4
Check: put x = 12 back into the equation.
$10\cdot12 - 9 = 120 - 9 = 111 \checkmark$

LaTeX source of the formulas on this page

\[ 10x - 9 = 111\ \Rightarrow\ x = 12 \]
\[ 10x - 9 = 111 \]
\[ 10x - 9 + 9 = 111 + 9 \ \Rightarrow\ 10x = 120 \]
\[ \frac{10x}{10} = \frac{120}{10} \ \Rightarrow\ x = 12 \]
\[ 10\cdot12 - 9 = 120 - 9 = 111 \checkmark \]

Trying values of x in 10x − 9 = 111

x	10x − 9	Equals 111?
10	91	no
11	101	no
12	111	yes
13	121	no
14	131	no

Questions

What is x in 10x − 9 = 111?

The solution of 10x − 9 = 111 is x = 12.

How do you solve 10x − 9 = 111?

Add 9 to both sides to get 10x = 120, then divide both sides by 10 to get x = 12.

How do I check the answer?

Replace x by 12: 10(12) − 9 = 111, which is 111.

Solve 10x − 9 = 111

How to work it out

Trying values of x in 10x − 9 = 111

Questions

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