a) 7 is a prime number so the only factor is 7.
b) 15 is a composite number.
We can start by dividing by 3 (as 2 is not a factor for 15), and get 5, that is a prime, so it ends there.
We can write 15 = 3 * 5
c) 19 is a prime number.
d) 17 is a prime number.
e) 4 is composite, and can be written as: 4 = 2 * 2
f) 8 is composite and can be written as 8 = 2 * 2 * 2
