Describe the following sets in Roster form:
{x N: x is a prime number, 10 < x < 20}
X is a natural number and is between 10 and 20.
X is such that x is a prime number between 10 and 20.
Prime numbers between 10 and 20 are 11,13,17,19.
∴ Roster form will be {11,13,17,19}.