There are few things more embarrassing than failing to outsmart a six-year-old, but the parents of this first-grader were left stumped by his math homework – as were many other adults after the problem got shared on Facebook.

The Holderness Family uploaded a photo of the devilishly difficult conundrum to their profile, adding that the question appeared on the 7th and final page of their son’s homework sheet, and that the previous six pages were considerably more straightforward.

Challenging kids to identify the missing letter in a grid, with each letter representing a number, the question appears too difficult for most grown-ups, let alone first-graders.

However, some have noted that the answer could be the letter J, which represents the number 14, as this ensures that the grid always adds up to 40 when the letters in each diagonal line are added together.