Answer: The lines are only parallel if these pairs of angles are of equal size:
Angle 1 ≡ Angle 5
Angle 2 ≡ Angle 6
Angle 3 ≡ Angle 7
Angle 5 ≡ Angle 8
Explanation:
All these angles follow a rule called corresponding angles. The rule goes that corresponding angles on parallel lines are equal. If the pairs of angles are equal, this must mean that the lines are parallel and vice versa.