Solve 12x + 7 = 115
The solution of 12x + 7 = 115 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 12:
- 4
Check: put x = 9 back into the equation.
LaTeX source of the formulas on this page
\[ 12x + 7 = 115\ \Rightarrow\ x = 9 \]
\[ 12x + 7 = 115 \]
\[ 12x + 7 - 7 = 115 - 7 \ \Rightarrow\ 12x = 108 \]
\[ \frac{12x}{12} = \frac{108}{12} \ \Rightarrow\ x = 9 \]
\[ 12\cdot9 + 7 = 108 + 7 = 115 \checkmark \]Trying values of x in 12x + 7 = 115
| x | 12x + 7 | Equals 115? |
|---|---|---|
| 7 | 91 | no |
| 8 | 103 | no |
| 9 | 115 | yes |
| 10 | 127 | no |
| 11 | 139 | no |
Questions
What is x in 12x + 7 = 115?
The solution of 12x + 7 = 115 is x = 9.
How do you solve 12x + 7 = 115?
Subtract 7 from both sides to get 12x = 108, then divide both sides by 12 to get x = 9.
How do I check the answer?
Replace x by 9: 12(9) + 7 = 115, which is 115.