i was given this question: Two cards are simultaneously drawn from an ordinary deck. The probability that they're not both the same suit is ....? and the guy who gave me the question said that the correct answer is 13/17 i am not really sure. i think it should be 16/17. anyone??

13/17 is correct. The problem is equivalent to 1 - probability that they are both the same suit. On the second draw, the probably that it's the same suit is 12/51 (12 cards left of that suit in the 51 remaining cards in the deck). 1 - 12/51 = 13/17. Or... On the second draw, you would have to draw one of the remaining 3*13=39 cards that aren't the same suit. 39/51 = 13/17