Answer
No
Work Step by Step
Using Pythagorean's Theorem...
$a^{2}+b^{2}=c^{2}$
Substitute in known lengths...
$11^{2}+8^{2}=15^{2}$
Simplify...
$121+64=225$
$185\ne225$
Since the leg lengths (squared) do not equal the hypotenuse (squared) then the triangle is not a right triangle.
