Math genius

There's something I haven't told you.  I'm a math genius.  Give me two single-digit numbers and I can add them in my head WITHOUT A CALCULATOR.

Five and three?  The answer is eight.

Seven and six?  The answer is eleven.

Seven and zero?  The answer is seven.

You'll notice that I produced the answers to all of those addition problems immediately.  That is because I was able to add the numbers in my head, using only my brain.  This is a rare skill found in only approximately 2 percent of all Americans.  I don't know how many percents that leaves for the rest, but I know it is at least nine (two plus nine equals only eleven percent).

Two plus six?  Eight.

Nine plus three?  That is, uh, twelve.

Please, stop quizzing me.  I can only answer so many addition problems -- then I become exhausted.  Although my math genius looks effortless, I can assure you, it's extremely mentally draining.  Imagine the most physically taxing thing you've ever done.  Now, add nine to it.  That's how exhausting addition is for me.  Maybe that thought experiment will give you a little more perspective when you pepper me incessantly with addition questions.

Seven plus ten?  No, I can't answer that.