Solve 8x + 7 = 79
The solution of 8x + 7 = 79 is x = 9.
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 7 from both sides:
- 3
Divide both sides by 8:
- 4
Check: put x = 9 back into the equation.
LaTeX source of the formulas on this page
\[ 8x + 7 = 79\ \Rightarrow\ x = 9 \]
\[ 8x + 7 = 79 \]
\[ 8x + 7 - 7 = 79 - 7 \ \Rightarrow\ 8x = 72 \]
\[ \frac{8x}{8} = \frac{72}{8} \ \Rightarrow\ x = 9 \]
\[ 8\cdot9 + 7 = 72 + 7 = 79 \checkmark \]Trying values of x in 8x + 7 = 79
| x | 8x + 7 | Equals 79? |
|---|---|---|
| 7 | 63 | no |
| 8 | 71 | no |
| 9 | 79 | yes |
| 10 | 87 | no |
| 11 | 95 | no |
Questions
What is x in 8x + 7 = 79?
The solution of 8x + 7 = 79 is x = 9.
How do you solve 8x + 7 = 79?
Subtract 7 from both sides to get 8x = 72, then divide both sides by 8 to get x = 9.
How do I check the answer?
Replace x by 9: 8(9) + 7 = 79, which is 79.