Solve 3x + 13 = 28
The solution of 3x + 13 = 28 is x = 5.
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 13 from both sides:
- 3
Divide both sides by 3:
- 4
Check: put x = 5 back into the equation.
LaTeX source of the formulas on this page
\[ 3x + 13 = 28\ \Rightarrow\ x = 5 \]
\[ 3x + 13 = 28 \]
\[ 3x + 13 - 13 = 28 - 13 \ \Rightarrow\ 3x = 15 \]
\[ \frac{3x}{3} = \frac{15}{3} \ \Rightarrow\ x = 5 \]
\[ 3\cdot5 + 13 = 15 + 13 = 28 \checkmark \]Trying values of x in 3x + 13 = 28
| x | 3x + 13 | Equals 28? |
|---|---|---|
| 3 | 22 | no |
| 4 | 25 | no |
| 5 | 28 | yes |
| 6 | 31 | no |
| 7 | 34 | no |
Questions
What is x in 3x + 13 = 28?
The solution of 3x + 13 = 28 is x = 5.
How do you solve 3x + 13 = 28?
Subtract 13 from both sides to get 3x = 15, then divide both sides by 3 to get x = 5.
How do I check the answer?
Replace x by 5: 3(5) + 13 = 28, which is 28.