In the diagram PQ is a straight line Calculate ... - WAEC Mathematics 2013 Question

Sum of angles on straight line = 180^o

80^o + 50^o + x + 10^o = 180^o

140^o + x = 180^o

x = 180^o - 140^o

x = 40^o

total sum of all angles = 360^o

2y^o + 2x^o + 80^o + 50^o + x + 10^o = 360^o

2y^o + 2(40)^o + 80^o + 50^o + 40 + 10 = 360^o

2y^o + 80 + 180^o = 360^o

2y^o + 260^o = 360^o

2y^o = 360^o - 260^o

2y^o = 100^o

angle 2y^o = 100^o