A logic puzzle that baffles adults can supposedly be solved by children in seconds.

The puzzle, from a Hong Kong primary school admission test for six-year-olds, is supposed to be solved in under 20 seconds.

The question baffling adults - but not children.

It has now gone viral, perhaps because of its absurd simplicity when actually worked out. (Spoiler: the answer is below, but try and figure it out on your own first!)

Based on the visible numbers in the image above students are asked to work out the number hidden by the parked car. The numbers - 16, 06, 68, 88, X, and 98 - don't exactly lead to any quick pattern recognition.