Data Sufficiency

sukhman wrote:If x and y are integers, is x(y+1) an even number?
1) x, and y are prime numbers.
2) y > 7

Having scanned the two statements, I can see that this question is ultimately testing whether or not we recognize that ALL prime numbers are odd EXCEPT for 2 (which is even).

Target question: Is x(y+1) an even number?

Statement 1: x and y are prime numbers.
There are several values of x and y that satisfy this condition. Here are two:
Case a: x = 2 and y = 3, in which case x(y+1) is EVEN
Case b: x = 3 and y = 2, in which case x(y+1) is ODD
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: y > 7
There are several values of x and y that satisfy this condition. Here are two:
Case a: x = 2 and y = 8, in which case x(y+1) is EVEN
Case b: x = 3 and y = 8, in which case x(y+1) is ODD
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
If y is a prime number and y > 7, we know that y MUST BE ODD
If y is odd, then y+1 must be EVEN
This means that x(y+1) = x(some EVEN integer) = EVEN
So, x(y+1) is definitely even
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer = C

Cheers,
Brent