Question

D F = 11 in.
FA = 5 in.
Find AD.

Answer 1

Pythagorean theorem (a^2 + b^2 = c^2) where a = 11 and b = 5. a and b are your two known sides and c (which is your hypotenuse) is what you are looking for. do you understand?

Answer 2

(Right Triangle ONLY!)
5²+11²=x²
25+121=x²
146=x²
√146=√x
√146=x