Final answer:
A zero pair is when two numbers add up to zero, such as +16 and -16, resulting in breaking even. However, in José's case, a net gain of 13 utils is observed rather than a zero pair, as he gains more utility from movies than he loses from giving up a T-shirt.
Step-by-step explanation:
The concept of a zero pair in mathematics refers to a pair of numbers that add up to zero, effectively canceling each other out. This is important in the context of breaking even because it illustrates a situation where gains and losses are equal, resulting in a net effect of zero. For example, if Juan has financial gains represented by +16 and financial losses represented by -16, these would form a zero pair, which means he neither makes a profit nor suffers a loss, hence breaking even.
Relating to the provided information about José, zero pairs are not directly relevant since he is experiencing a net gain rather a break-even situation. When José moves from point P to point Q, he is gaining 31 utils from movies and losing 18 utils from a T-shirt, which results in a net gain of 13 utils, not a zero pair. Therefore, José's situation is advantageous because the total utility at Q is greater than the total utility at P, endorsing the decision to give up the fourth T-shirt to buy two movies.