Which value makes it true?
The question
3x − 6 = 9
Which value of x makes 3x − 6 = 9 true?
Try each value and see which one works
3456
x = 33 × 3 − 6= 3
3=9false
x = 43 × 4 − 6= 6
6=9false
x = 53 × 5 − 6= 9
9=9true
x = 5
- 3x − 6 = 9 is true for only one of these values. Try each one.
- Try x = 3. 3 × 3 − 6 = 3. 3 is not 9, so x = 3 does not work.
- Try x = 4. 3 × 4 − 6 = 6. 6 is not 9, so x = 4 does not work.
- Try x = 5. 3 × 5 − 6 = 9. 9 really is 9, so x = 5 makes it true.
- Only one value makes it true, so that is the solution.
How it works.
- 01
3x − 6 = 9 is true for only one of these values. Try each one.
- 02
Try x = 3. 3 × 3 − 6 = 3. 3 is not 9, so x = 3 does not work.
- 03
Try x = 4. 3 × 4 − 6 = 6. 6 is not 9, so x = 4 does not work.
- 04
Try x = 5. 3 × 5 − 6 = 9. 9 really is 9, so x = 5 makes it true.
- 05
Only one value makes it true, so that is the solution.