Solve 3x + 3 = 15
The solution of 3x + 3 = 15 is x = 4.
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 3:
- 4
Check: put x = 4 back into the equation.
LaTeX source of the formulas on this page
\[ 3x + 3 = 15\ \Rightarrow\ x = 4 \]
\[ 3x + 3 = 15 \]
\[ 3x + 3 - 3 = 15 - 3 \ \Rightarrow\ 3x = 12 \]
\[ \frac{3x}{3} = \frac{12}{3} \ \Rightarrow\ x = 4 \]
\[ 3\cdot4 + 3 = 12 + 3 = 15 \checkmark \]Trying values of x in 3x + 3 = 15
| x | 3x + 3 | Equals 15? |
|---|---|---|
| 2 | 9 | no |
| 3 | 12 | no |
| 4 | 15 | yes |
| 5 | 18 | no |
| 6 | 21 | no |
Questions
What is x in 3x + 3 = 15?
The solution of 3x + 3 = 15 is x = 4.
How do you solve 3x + 3 = 15?
Subtract 3 from both sides to get 3x = 12, then divide both sides by 3 to get x = 4.
How do I check the answer?
Replace x by 4: 3(4) + 3 = 15, which is 15.