Supposedly only 1 in a 1000 get it right. I reckon that average would be a lot higher from the members on here.
There are actually two possible solutions. (I got the first one right but didn't have the patience to look at the second solution, lol)
1+4 = 5
2+5 = 12
3+6 = 21
8+11 = ?
Don't leave your answers! I will provide the link so you can check if you got one or both right!
good luck
http://www.msn.com/en-gb/news/offbeat/a-viral-math-question-that-has-2-solutions-is-stumping-the-internet/ar-BBEFtXP?li=AA9SkIr&ocid=spartanntp
There are actually two possible solutions. (I got the first one right but didn't have the patience to look at the second solution, lol)
1+4 = 5
2+5 = 12
3+6 = 21
8+11 = ?
Don't leave your answers! I will provide the link so you can check if you got one or both right!
good luck

http://www.msn.com/en-gb/news/offbeat/a-viral-math-question-that-has-2-solutions-is-stumping-the-internet/ar-BBEFtXP?li=AA9SkIr&ocid=spartanntp