Use Pythagorean theorem to help solve this problem.
a = 16
b = 12
c = hypotenuse
a^2 + b^2 = c^2. Plug in your numbers.
(16)^2 + (12)^2 = c^2. Square both 12 and 16
256 + 144 = c^2. Add together a and b
400 = c^2. Take the square root of both sides.
20 = c.