The sum of the digits of a two-digit number is 15 and the difference between the digits is 3. What is the two-digit number?

Answer: Option D

Let the ten's digit be x and unit's digit be y
Then, x + y = 15 and x - y = 3   or   y - x = 3
Solving x + y = 15   and   x - y = 3, we get: x = 9, y = 6
Solving x + y = 15   and   y - x = 3, we get: x = 6, y = 9
So, the number is either 96 or 69
Hence, the number cannot be determined.