Since the sum of the three angles of any triangle is 180°, we have that the third angle is 180° - (30°+50°) = 180° - 80° = 100° I'll arbitrarily let angle A = 30°, angle B = 100°, and angle C = 50°By the law of sines, Perimeter = a + b + c = 20, so substituting in , ----- Edwin