Question 413751
11.
For the difference between two real numbers to be 0, the numbers have to be must be equal. Therefore, for the digits of a two digit number to have a difference of zero, the digits must be equal. This number is less than 20 and greater than 10.
Therefore, the tens place must have a one in it. Since the tens place is 1, then the ones place must also be 1. So, we come to the answer "11."