The answer will be 1/2 because in a coin there is heads and tails. So, its 50% chance to get either one. Now, for 2 coins there will be heads, tails, head, and tails. The question ask you for tails so there are 2 ways to get tails. Also, the total of the two coins to get either heads or tail is 4. You should get 2/4 which is 1/2.