Step-by-step explanation:
Pythagoras :
c² = a² + b²
c is the Hypotenuse (the side opposite of the 90° angle).a and b are the legs of the right-angled triangle.
so,
x² + 12² = (x + 8)² = x² + 16x + 64
144 = 16x + 64
16x = 80
x = 5
