You don’t have to be a math whiz to know that 4 - 2 + 1 equals 3. Yet I was working with several students recently who said it equals 1. And it wasn’t their fault. Nor was it their teacher’s fault.

A graphic artist is testing everyone’s knowledge of the mathematical order of operations with a string of numbers and missing arithmetic symbols. Gergely Dudás, of Budapest, Hungary, shared the new ...