Answer: comparison postulate.
Explanation.
The given inequality might be either 3 + 2 > 5 or 2 + 2 < 5. The reasoning and the result is the same for effects of this question.
The comparison postulate states that one and only one of the following statements is true: a = b, a > b, a < b.
This is, a is either equal, or greater than or less than b, but not equal and greater, or equal and less, or greater and less. One and only one of them is true.
So, since 3 + 2 = 5, the comparison postulate assures that the inequality cannot both be true. This is 3 + 2 is equal to 5, and not greater or less than 5.