If U={natural numbers less than 20} and N={factors of 18}, what is N’?

Question

What am I supposed to do?

I know the factors of 18 are 1, 2,3,6, 9, & 18.
I know the natural numbers less than 20 are 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20. So what am I supposed to be looking for?

Thank you!

Answer 1

N' is the notation for "N compliment"
or "not N"
so in your list for U, which numbers are NOT factors of 18 ?

Answer 2

natural number that are less than 18

Answer 3

even number are

Answer 4

Thanks