If the subject is singular, then the pronouns referring to the subject should be singular as well.

Ex. I, he, she, it, every, each, everyone, none, whoever, someone, nobody, either neither, someone etc. Sets of integers that satisfy the Pythagorean Theorem

Examples include: (3, 4, 5), (5, 12, 13), (6, 8, 10), (7, 24, 25) ;