1. 
a. 0 + 3 + 6 + 9 = 18
b. 0 (it goes through the loop once, but i is 0 the first time through the loop)
c. 0 + 3 + 6 + 9 = 18 (on the next iteration, i = 12, which is NOT < num)

2.

i. function should return an int not a boolean
ii. sum needs to have a type
iii. don't forget your semi-colons!

int stringLengths(String s1, String s2){
	int sum = 0;
	sum = s1.length() + s2.length();
	return sum;
}

(this could also be written as a single line function :)