A picture circulating online challenged people to determine the missing number from what looked like a simple sequence of numbers from 1 to 19. "Which number is missing?" the puzzle asks.

In this puzzle, numbers are positioned at the corners and inside the triangles. Your task is to find the relationship between these numbers and figure out the missing value in the final triangle.

Puzzles9 shared a brain teaser with nine squares, one missing a number. The challenge is to figure out how the numbers are related and fill in the missing one. Can you solve it?