The Secret Behind the Math
At first glance, the equation looks completely broken. In regular arithmetic, eleven plus two is thirteen, not one. However, the secret to solving this riddle lies in changing your perspective from a calculator to something you look at every single day: a clock.
When you think about time, the riddle makes perfect sense. If it is 11 o'clock and you add 2 hours, the clock moves forward to 1 o'clock.
Following that exact same logic, we can easily solve the second part of the riddle:
Start at 9 o'clock.
Add 5 hours to the time.
Counting forward (10, 11, 12, 1, 2), you land exactly on 2 o'clock.
Therefore, nine plus five equals two!