Solve 8x − 9 = 79

The solution of 8x − 9 = 79 is x = 11.

8x - 9 = 79\ \Rightarrow\ x = 11

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The lines y = 8x − 9 and y = 79 meet at x = 11. 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.
$8x - 9 = 79$
2
Add 9 to both sides:
$8x - 9 + 9 = 79 + 9 \ \Rightarrow\ 8x = 88$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{88}{8} \ \Rightarrow\ x = 11$
4
Check: put x = 11 back into the equation.
$8\cdot11 - 9 = 88 - 9 = 79 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 9 = 79\ \Rightarrow\ x = 11 \]
\[ 8x - 9 = 79 \]
\[ 8x - 9 + 9 = 79 + 9 \ \Rightarrow\ 8x = 88 \]
\[ \frac{8x}{8} = \frac{88}{8} \ \Rightarrow\ x = 11 \]
\[ 8\cdot11 - 9 = 88 - 9 = 79 \checkmark \]

Trying values of x in 8x − 9 = 79

x	8x − 9	Equals 79?
9	63	no
10	71	no
11	79	yes
12	87	no
13	95	no

Questions

What is x in 8x − 9 = 79?

The solution of 8x − 9 = 79 is x = 11.

How do you solve 8x − 9 = 79?

Add 9 to both sides to get 8x = 88, then divide both sides by 8 to get x = 11.

How do I check the answer?

Replace x by 11: 8(11) − 9 = 79, which is 79.

Solve 8x − 9 = 79

How to work it out

Trying values of x in 8x − 9 = 79

Questions

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