Composite Question 10 from "(I'm Overwhelmed) Arithmetic Progress Quiz #2" [6807]

https://www.gregmat.com/quizzes/quiz/im-overwhelmed-arithmetic-progress-quiz-2 (Question 10)


Why is there a composite question!?

I spent about an hour trying to ace this and then searched up whether composite questions are on the GRE, and it said no :confused:

What’s the source because ETS definitely can test questions on composite numbers.

Ets math review guide.