Solve 10x − 9 = 71

The solution of 10x − 9 = 71 is x = 8.

10x - 9 = 71\ \Rightarrow\ x = 8

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The lines y = 10x − 9 and y = 71 meet at x = 8. 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.
$10x - 9 = 71$
2
Add 9 to both sides:
$10x - 9 + 9 = 71 + 9 \ \Rightarrow\ 10x = 80$
3
Divide both sides by 10:
$\frac{10x}{10} = \frac{80}{10} \ \Rightarrow\ x = 8$
4
Check: put x = 8 back into the equation.
$10\cdot8 - 9 = 80 - 9 = 71 \checkmark$

LaTeX source of the formulas on this page

\[ 10x - 9 = 71\ \Rightarrow\ x = 8 \]
\[ 10x - 9 = 71 \]
\[ 10x - 9 + 9 = 71 + 9 \ \Rightarrow\ 10x = 80 \]
\[ \frac{10x}{10} = \frac{80}{10} \ \Rightarrow\ x = 8 \]
\[ 10\cdot8 - 9 = 80 - 9 = 71 \checkmark \]

Trying values of x in 10x − 9 = 71

x	10x − 9	Equals 71?
6	51	no
7	61	no
8	71	yes
9	81	no
10	91	no

Questions

What is x in 10x − 9 = 71?

The solution of 10x − 9 = 71 is x = 8.

How do you solve 10x − 9 = 71?

Add 9 to both sides to get 10x = 80, then divide both sides by 10 to get x = 8.

How do I check the answer?

Replace x by 8: 10(8) − 9 = 71, which is 71.

Solve 10x − 9 = 71

How to work it out

Trying values of x in 10x − 9 = 71

Questions

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