Solve 8x − 13 = 91

The solution of 8x − 13 = 91 is x = 13.

8x - 13 = 91\ \Rightarrow\ x = 13

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The lines y = 8x − 13 and y = 91 meet at x = 13. 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.
$8x - 13 = 91$
2
Add 13 to both sides:
$8x - 13 + 13 = 91 + 13 \ \Rightarrow\ 8x = 104$
3
Divide both sides by 8:
$\frac{8x}{8} = \frac{104}{8} \ \Rightarrow\ x = 13$
4
Check: put x = 13 back into the equation.
$8\cdot13 - 13 = 104 - 13 = 91 \checkmark$

LaTeX source of the formulas on this page

\[ 8x - 13 = 91\ \Rightarrow\ x = 13 \]
\[ 8x - 13 = 91 \]
\[ 8x - 13 + 13 = 91 + 13 \ \Rightarrow\ 8x = 104 \]
\[ \frac{8x}{8} = \frac{104}{8} \ \Rightarrow\ x = 13 \]
\[ 8\cdot13 - 13 = 104 - 13 = 91 \checkmark \]

Trying values of x in 8x − 13 = 91

x	8x − 13	Equals 91?
11	75	no
12	83	no
13	91	yes
14	99	no
15	107	no

Questions

What is x in 8x − 13 = 91?

The solution of 8x − 13 = 91 is x = 13.

How do you solve 8x − 13 = 91?

Add 13 to both sides to get 8x = 104, then divide both sides by 8 to get x = 13.

How do I check the answer?

Replace x by 13: 8(13) − 13 = 91, which is 91.

Solve 8x − 13 = 91

How to work it out

Trying values of x in 8x − 13 = 91

Questions

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