Solve 8x − 9 = 55

The solution of 8x − 9 = 55 is x = 8.

8x - 9 = 55\ \Rightarrow\ x = 8

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The lines y = 8x − 9 and y = 55 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.
$8x - 9 = 55$
2
Add 9 to both sides:
$8x - 9 + 9 = 55 + 9 \ \Rightarrow\ 8x = 64$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{64}{8} \ \Rightarrow\ x = 8$
4
Check: put x = 8 back into the equation.
$8\cdot8 - 9 = 64 - 9 = 55 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 9 = 55\ \Rightarrow\ x = 8 \]
\[ 8x - 9 = 55 \]
\[ 8x - 9 + 9 = 55 + 9 \ \Rightarrow\ 8x = 64 \]
\[ \frac{8x}{8} = \frac{64}{8} \ \Rightarrow\ x = 8 \]
\[ 8\cdot8 - 9 = 64 - 9 = 55 \checkmark \]

Trying values of x in 8x − 9 = 55

x	8x − 9	Equals 55?
6	39	no
7	47	no
8	55	yes
9	63	no
10	71	no

Questions

What is x in 8x − 9 = 55?

The solution of 8x − 9 = 55 is x = 8.

How do you solve 8x − 9 = 55?

Add 9 to both sides to get 8x = 64, then divide both sides by 8 to get x = 8.

How do I check the answer?

Replace x by 8: 8(8) − 9 = 55, which is 55.

Solve 8x − 9 = 55

How to work it out

Trying values of x in 8x − 9 = 55

Questions

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