If you’ve ever fantasized about how much easier life would be if you could go back to elementary school, this math problem may give you second thoughts. The question first appeared on a web forum, Mashable reports, and after recently resurfacing, it’s been perplexing adults across social media.

According to the original poster AlmondShell, the bonus question was given to primary one, or first grade students, in Singapore. It instructs readers to “study the number pattern” and “fill in the missing numbers.” The puzzle, which comprises five numbers and four empty circles waiting to be filled in, comes with no further explanation.

Some forum members commented with their best guesses, while others expressed disbelief that this was a question on a kid’s exam. Commenter karrotguy illustrates one possible answer: Instead of looking for complex math equations, they saw that the figure in the middle circle (three) equals the amount of double-digit numbers in the surrounding quadrants (18, 10, 12). They filled out the puzzle accordingly.

A similar problem can be found on the blog of math enthusiast G.R. Burgin. His solution, which uses simple algebra, gets a little more complicated.

The math tests given to 6- and 7-year-olds in other parts of the world aren’t much easier. If your brain isn’t too worn out after the last one, check out this maddening problem involving trains assigned to students in the UK.

[h/t Mashable]