Since this triangle is a right triangle, we can use the pythagorean theorem which is a^2 +b^2 = c^2 (where a is the legs of the triangle and c is the hypotenuse.) For this triangle using the pythagorean theorem we can say that 12^2 +16^2 = x^2. When we simplify this equation we get 144+256=x^2. When we simplify this we get x^2=400. When we take the square root of x we get that x = √400 = 20. The answer is (D) 20.
