Another puzzle has been doing the rounds on the internet - leaving scores of people flummoxed in its wake.
It was posted online by Facebook user Antley Lamont Staten accompanied by the words: "Ok I don't get it?".
Since then it's been shared nearly 400,000 times on Facebook alone, and countless valiant attempts have been made to solve the simple-looking number puzzle.
One user volunteered: "It's 4 and 5. 3+6=9 2+5=7 not 8 and 1+4=5 not 7. That's how I looked at it."
We won't spoil your fun, but suffice to say the answer is not where you think it should be.
And if you give up, a quick peek at the comments below will provide the answer and soothe your tortured brain.