x = 30^o (alternate ∠s b/c PQ//Sr)
Y = 50^o (vertical opposite ∠s)
r = 30^o (alternate ∠s b/c PQ//SR)
But = y + q + t = 180^o (∠s on a straight line)
50 + q + 30 = 180
q + 80 = 180
q = 180 -80
q = 100^o