Divisibility and Primes from 5lb book

![Screen Shot 2021-05-27 at 4.55.30 PM|690x460](upload://4II6v8hHA6Z1J3JXKEzmMyjuivf.jpeg) 

Was just wondering how to solve this problem thanks!!

I don’t know if it’s just me, but your picture isn’t showing. Maybe tell us what chapter and number it is.