Check out the attached image. We have a right triangle with legs of 12 and 16. The hypotenuse is x
a = 12
b = 16
c = x
Pythagorean Theorem
a^2 + b^2 = c^2
12^2+16^2 = x^2
144 + 256 = x^2
400 = x^2
x^2 = 400
x = sqrt(400) ... 'sqrt' stands for 'square root'
x = 20
Answer: Choice D) 20
