A basic DS concept question

mandhan wrote:Hello,
I have this basic confusion about DS questions on GMAT. Please comment.

1) Is x = 3?

a) x = 1 OR x = 3
b) x = 2 OR x = 3
I think the answer should be E.

2) What is x?

a) x = 1 OR x = 3
b) x = 2 OR x = 3
I think the answer should be C.

What do you think?

Shouldn't they both be C? Since a) says 1 or 3 and b) says 2 or 3, combining the two only yields one possible value.

That is what I had thought until I came across this problem:
https://gmatclub.com/forum/m01-71305.html

Quoting from that thread:
"In data sufficiency with "is...?" questions we should arrive at either YES or NO. We cannot have both answers (ie) YES and NO from a single statement."

I came up with the above 2 questions to clear this concept.

Can experts throw some light please? The main doubt is with the first question. I think its E..

If there is only one answer that satisfies both statements then that is the correct answer.

Another basic question on DS. I read that if it's not clearely mentioned we should check the answer by substituting -ve or 0. But when I do that in this question my answer is not matching Official answer.
Below questions is from OG12.

Q- If i and j are integers, is i+j an even number?
1. i<10
2. i=j
OA is B

My answer was E since if we substitute 0 for i, we can't tell if it is even or zero. It is definately not odd but it is not sufficient to decide if it is even. Please help. Am I doing it wrong by considering 0 in the example.

Zero is an even number. It is neither positive nor negative, but it is even.

Tani,
Thanks for your reply. That explains the answer.

I have read that zero is neither odd nor even and hence the confusion.
One more question.

is -3 odd ? or are negative numbers odd or even?

'-3' is negative and odd. Negative numbers can still be odd, even, an integer, etc.