Solve 9x − 8 = 91

The solution of 9x − 8 = 91 is x = 11.

9x - 8 = 91\ \Rightarrow\ x = 11

Explain it step by step in chat Make a short video of it

The lines y = 9x − 8 and y = 91 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.
$9x - 8 = 91$
2
Add 8 to both sides:
$9x - 8 + 8 = 91 + 8 \ \Rightarrow\ 9x = 99$
3
Divide both sides by 9:
$\frac{9x}{9} = \frac{99}{9} \ \Rightarrow\ x = 11$
4
Check: put x = 11 back into the equation.
$9\cdot11 - 8 = 99 - 8 = 91 \checkmark$

LaTeX source of the formulas on this page

\[ 9x - 8 = 91\ \Rightarrow\ x = 11 \]
\[ 9x - 8 = 91 \]
\[ 9x - 8 + 8 = 91 + 8 \ \Rightarrow\ 9x = 99 \]
\[ \frac{9x}{9} = \frac{99}{9} \ \Rightarrow\ x = 11 \]
\[ 9\cdot11 - 8 = 99 - 8 = 91 \checkmark \]

Trying values of x in 9x − 8 = 91

x	9x − 8	Equals 91?
9	73	no
10	82	no
11	91	yes
12	100	no
13	109	no

Questions

What is x in 9x − 8 = 91?

The solution of 9x − 8 = 91 is x = 11.

How do you solve 9x − 8 = 91?

Add 8 to both sides to get 9x = 99, then divide both sides by 9 to get x = 11.

How do I check the answer?

Replace x by 11: 9(11) − 8 = 91, which is 91.

Solve 9x − 8 = 91

How to work it out

Trying values of x in 9x − 8 = 91

Questions

Similar equations