You can use the Pythagorean theorem to answer this. The diagonal is the hypotenuse of the right triangle that is formed. So, your equation will look like (h is height):
[tex]34^2+h^2 = 39^2[/tex]
We have to solve for h:
[tex]h^2 = 39^2-34^2[/tex]
[tex]h = \sqrt{39^2-34^2} [/tex]
You can plug it into a calculator, and you get approximately 19.105. The answer closest to that is B. So, that's your answer! Hope it helps. If anything doesn't make sense, hmu!
