Find x if sides of a right triangle are 9, x and 15 with 15 the hypotenuse.

1. By the theorem 9^2 + x^2 = 15^2. 2. 81 + x^2 = 225. 3. x^2 = 144, so x = 12. 4. Hence x = 12. _Source: Selina Concise Mathematics Class 9, Ch on Pythagoras Theorem (Mistral OCR'd PDF), section on numerical example_