have to find the side length of x for the following right triangle?

Answer:
x = 9
Step-by-step explanation:
[tex]\sf (leg_1)^2 + (leg_2)^2 = hypotenuse^2[/tex]
[tex]x^{2} + 12^2 = 15^2\\\\x^{2} + 144 = 225[/tex]
x² = 225 - 144
x² = 81
x² = 9²
x = 9
[tex]\boxed{x = 9}[/tex]