(1) Of Sheila’s show dogs, exactly 3 have won prizes of at least $500.
Total = Dogs who won prize money equal to and greater than $500 + Dogs who won Prize money less than $500
But we don't have information exactly how many didn't won any prize money or prize money less than 500$
(Insufficient)

(2) Of Sheila’s show dogs, exactly 40% have not won a prize of $500 or more.
40% haven't won a prize equal to or greater than $500
But (40% of what no.?)
No exact no. Is given to determine the total no. Of Dogs.
(Insufficient)

Combining both:
60% who won prize money equal to or greater than 500$ = 3
So 40% who didn't won that much prize money = 2
Total no. Of dogs = 5
(Sufficient)

Answer is C

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VERITAS PREP OFFICIAL SOLUTION:

Question Type: What Is the Value? This question asks for the specific number of show dogs.

Statement 1: Exactly 3 of the dogs won prizes of at least $500. This statement is not sufficient alone. There is no way for you to determine the total number of show dogs. Eliminate choices A and D.

Statement 2: 40% of the dogs have not won a prize of $500 or more. This statement is also not sufficient alone. As in Statement 1, there is no way to determine the total number of dogs. Eliminate choice B.

Together: One of the best ways to solve a GMAT problem is to find a way to state the same thing in two different ways, allowing you to create an equation. You know from Statement 1 that 3 dogs have won prizes of $500 or more and you know from Statement 2 that 60% of the dogs have won a prize of $500 or more. So that means “3 dogs = 60% of the total dogs” or “3 = .6d” She has 5 show dogs total. This information is sufficient and the correct answer is C.
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