DS Problems - Two solutions for a variable = insufficient?

[burns.nelson]

Algebra Strategy Guide, Chapter 6, Quadratic Equations, Problem Set, Page 89, Question #5:

5. What is x?

(1) x = 4y - 4
(2) xy = 8

After combining both equations, I'm able to determine that there are two solutions for x. Therefore, I chose C as my answer. However, E is correct. Must we always have only ONE solution for a variable in DS questions for a statement(s) to be sufficient?

[tim]

Quick recap on how to determine sufficiency versus insufficiency on DS:

There is always a question at the top of the page; focus on that and figure out how many answers there are.

If you can get two or more answers, the information you are using is insufficient (this is the case you refer to)

If you can get only one answer, the information you are using is sufficient

If you cannot get any answers, you have done something wrong. DO NOT ASSUME INSUFFICIENCY! There will ALWAYS be at least one possible answer to the question at the top of the page; the real question is whether there is a second possible answer.

[burns.nelson]

That's pretty simple - thank you!

[tim]

Glad to help!