The angle does not matter. Think of it as finding the other side to a triangle. Use

a=39 (line AB)
b=b (the leg we need to find)
c=89 (line BD)


(subtract the 1521 from both sides)

(square root both sides)

b = 80
AD=80
Answer:
41
Step-by-step explanation:
putting x into the eqn
(-7)*(2/5 + (-3/7))
= -14/5 + 3
=1/5