Solve 10x + 1 = 81
The solution of 10x + 1 = 81 is x = 8.
How to work it out
- 1
The goal is to get x alone. Undo the operations in the opposite order: first the addition, then the multiplication.
- 2
Subtract 1 from both sides:
- 3
Divide both sides by 10:
- 4
Check: put x = 8 back into the equation.
LaTeX source of the formulas on this page
\[ 10x + 1 = 81\ \Rightarrow\ x = 8 \]
\[ 10x + 1 = 81 \]
\[ 10x + 1 - 1 = 81 - 1 \ \Rightarrow\ 10x = 80 \]
\[ \frac{10x}{10} = \frac{80}{10} \ \Rightarrow\ x = 8 \]
\[ 10\cdot8 + 1 = 80 + 1 = 81 \checkmark \]Trying values of x in 10x + 1 = 81
| x | 10x + 1 | Equals 81? |
|---|---|---|
| 6 | 61 | no |
| 7 | 71 | no |
| 8 | 81 | yes |
| 9 | 91 | no |
| 10 | 101 | no |
Questions
What is x in 10x + 1 = 81?
The solution of 10x + 1 = 81 is x = 8.
How do you solve 10x + 1 = 81?
Subtract 1 from 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) + 1 = 81, which is 81.