The triangle sum theorem says all 3 interior angles must equal 180 degrees.
so, 43 + 35 = 78. [ 180 - 78 = 102 degrees for the missing angles shared by the 2 triangles.
102 + 18 = 120. [180 - 120 = 60}
leaving the measure of Angle A as 60 degrees.
The answer to the question is c
Answer: number 2
Step-by-step explanation:
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