Answer:
50 + 3n = 100
∠D= 87°, ∠E = 50°
Sum of three angles in a triangle is 180°
∠F = 180 - (∠D + ∠E)
∠F = 180 - (87 + 50)
∠F = 180 - 137
∠F = 43°
Side opposite to greatest angle is the longest side.
Among angle D, E and F, angle D is the greatest angle
So side opposite to angle D is the longest side which is EF
Option B is the answer
