The sum of angles is 180°, so angle B can be found from
83°20' + ∠B + 54°36' = 180°
∠B = 180° - 137°56'
∠B = 42°4'
The law of sines can be used to find the other sides.
a = c/sin(C)*sin(A) = 18.1/sin(54.6°)*sin(83°20')
a ≈ 22.1
b = c/sin(C)*sin(B) = 18.1/sin(54.6°)*sin(42°4')
b ≈ 14.9
