Solve 8x + 3 = 123
The solution of 8x + 3 = 123 is x = 15.
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 3 from both sides:
- 3
Divide both sides by 8:
- 4
Check: put x = 15 back into the equation.
LaTeX source of the formulas on this page
\[ 8x + 3 = 123\ \Rightarrow\ x = 15 \]
\[ 8x + 3 = 123 \]
\[ 8x + 3 - 3 = 123 - 3 \ \Rightarrow\ 8x = 120 \]
\[ \frac{8x}{8} = \frac{120}{8} \ \Rightarrow\ x = 15 \]
\[ 8\cdot15 + 3 = 120 + 3 = 123 \checkmark \]Trying values of x in 8x + 3 = 123
| x | 8x + 3 | Equals 123? |
|---|---|---|
| 13 | 107 | no |
| 14 | 115 | no |
| 15 | 123 | yes |
| 16 | 131 | no |
| 17 | 139 | no |
Questions
What is x in 8x + 3 = 123?
The solution of 8x + 3 = 123 is x = 15.
How do you solve 8x + 3 = 123?
Subtract 3 from both sides to get 8x = 120, then divide both sides by 8 to get x = 15.
How do I check the answer?
Replace x by 15: 8(15) + 3 = 123, which is 123.