Solve 3x + 13 = 7
The solution of 3x + 13 = 7 is x = -2.
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 = -2 back into the equation.
LaTeX source of the formulas on this page
\[ 3x + 13 = 7\ \Rightarrow\ x = -2 \]
\[ 3x + 13 = 7 \]
\[ 3x + 13 - 13 = 7 - 13 \ \Rightarrow\ 3x = -6 \]
\[ \frac{3x}{3} = \frac{-6}{3} \ \Rightarrow\ x = -2 \]
\[ 3\cdot(-2) + 13 = -6 + 13 = 7 \checkmark \]Trying values of x in 3x + 13 = 7
| x | 3x + 13 | Equals 7? |
|---|---|---|
| -4 | 1 | no |
| -3 | 4 | no |
| -2 | 7 | yes |
| -1 | 10 | no |
| 0 | 13 | no |
Questions
What is x in 3x + 13 = 7?
The solution of 3x + 13 = 7 is x = -2.
How do you solve 3x + 13 = 7?
Subtract 13 from both sides to get 3x = -6, then divide both sides by 3 to get x = -2.
How do I check the answer?
Replace x by -2: 3(-2) + 13 = 7, which is 7.