In the figure shown, lines l and m are parallel and lines r and t are transversals. Find x.
∠AOC+105∘=180∘ [Co-interior angles]
Hence, ∠AOC=180∘−105∘=75∘ (1 marks)
∠AOB=120∘ [Corresponding angles]
∠AOB=∠AOC+∠BOC (1 marks)
⇒120∘=75∘+x
⇒x=120∘−75∘=45∘ (1 marks)