Under the given condition, < A + < E = 180°. Hence, < B + < C + < d = 540° - 180° = 360°. Also, < B = 7x, < C = 3x and < D = 8x, where unknown "x" is the common measure of these 3 angles. So we have 7x + 3x + 8x = 360°, which implies x = 360/18 = 20°. Answer. < B = 7x = 140°; < C = 3x = 60°; < D = 8x = 160°.