Internet puzzles tend to drive people to the brink of insanity.

Facebook user recently posted a photo of a puzzle that was clearly making his head hurt:

“Ok I don’t get it?” he wrote as a comment — and he wasn’t alone. Since Staten posted the confounding conundrum, it has been shared almost 400,000 times with others trying to figure out WTF the answer to this mysterious math problem is.

Some took a stab at it.

“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,” one commenter wrote.

Another commenter who, after assumedly pulling out a handful of hair while trying to figure it out, proclaimed this after solving it:

“Omg. Took me a while because I was concentrating on the #’s lol.”

Thing is, that’s the trick. It’s actually not a math problem at all.