Write the following sets in roster from:

Prime number = Those number which is divisible by 1 and the number itself.

Prime numbers are 2, 3, 5, 7, 11, 13, …

Divisor of 42 :

$42=1 \times 42$

$42=2 \times 21$

$42=3 \times 14$

$42=6 \times 7$

So, divisors of 42 are 1, 2, 3, 6, 7, 14, 21, 42

The elements which are prime and divisor of 42 are 2, 3, 7

So, E = {2, 3, 7}