Question

What is the length of side x in this right triangle?

Answer 1

We use the Pythagorean theorem because it is a rectangle triangle. 
For that, x is the hypotenuse (c in the equation).
x^2= 8^2 + 15^2
x^2= 64 + 225
x^2= 289
x= $\sqrt289}$
x= 17