The existence of irrational numbers is best explained with an isosceles right triangle—that is, a triangle with two sides of an equal length that form a right angle.

The number 153 is the 17th triangular number: this means that if you add the numbers from 1 to 17, you get 153. If you were to divide the 153 into equal points, you could form an equilateral triangle.

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.