A Simple Math Puzzle Sparked a Viral Self-Test on X

A seemingly easy math problem posted on X by user @onlyskypace went viral after it was framed as a test of intelligence. The image showed a fraction with the sum of the square root of 49 and the square root of 9 over the square root of x, equal to 5, and asked what x is. The post drew more than 2.5 million views, thousands of likes, hundreds of quotes, and more than 15,000 replies.

The replies quickly turned into a showcase of confusion, with users giving answers including 4, 25, 9, 12, 5, 2, and even 92. Some people posted fully worked solutions, while others appeared to guess or misread the order of operations. Fast solvers boasted that it took them only five seconds, while others were mocked for getting it wrong, and some users said the thread itself was frightening.

The correct solution is x = 4. First, the square root of 49 is 7 and the square root of 9 is 3, which makes 10 in the numerator. That leaves 10 divided by the square root of x equal to 5, so the square root of x must be 2, and x must be 4.

The article says the main mistake was reading the equation too quickly, especially by treating only the 3 as being divided by the square root of x instead of the whole sum. It also notes that some users saw the wrong answers as part of a familiar engagement tactic, where easy questions are posted so people will answer, argue, and correct one another, driving more responses and visibility.