Respuesta :

harpazo
See picture.

We are looking for x.

x^2 + 6^2 = 12^2

x^2 + 36 = 144

x^2 = 144 - 36

x^2 = 108

sqrt{x^2} = sqrt{108}

x = sqrt{108}

You can break down the square of 108 if needed.
Ver imagen harpazo