The unknown side length for the right triangle x is equal to 17.
How to evaluate for the unknown side length of the right triangle.
The Pythagoras rule states that in a right-angled triangle, the square of the hypotenuse(the longest side) is equal to the sum of the squares of the other two sides.
For triangle we solve for x as follows:
using Pythagoras rule;
x² = 8² + 15²
x² = 64 + 225
x² = 289
x = √298 {take square root of both sides}
x = 17
Therefore, the unknown side lengths for the right triangle is x = 17