Combine the following statements using "if and only if'
p: if the sum of digit of a number is divisible by3, then the numebr is divisible by 3.

Given below are two pairs of statements. Combine these two statements using if and only if : p : If the sum of digits of a number is divisible by 3, then the number is divisible by 3. q : If a number is divisible by 3, then the sum of its digits is divisible by 3.

How many two-digit numbers are divisible by 3?