The Law of Detachment states the following:
If p → q is true, and p is true, then q is true.
An example of this law would be:
statements:
- If it's raining, the floor is wet.
- It's raining.
Conclusion:
- The floor is wet.
In the given problem, we have the statements:
- If x = 3, then 3x - 4 = 5.
- x = 3.
So we can write the conclusion using the law:
- 3x - 4 = 5.
Therefore the correct option is the third one.