Complete the following statements to prove that ∠IKL and ∠JLD are supplementary angles. It is given that ∠EIJ ≅ ∠GJI. Also, ∠EIJ ≅ ∠IKL and ∠GJI ≅ ∠JLK, as they are corresponding angles for parallel lines cut by a transversal. By the definition of congruent angles, m∠EIJ = m∠GJI, m∠EIJ = m∠IKL, and m∠GJI = m∠JLK. So, m∠IKL = m∠JLK by the (substitution property of equality, subtraction property of equality , or symmetry property of equality.) . Angle JLK and ∠JLD are supplementary angles by the (vertical angles theorem, congruent supplements theroem, or linear pair theroem.) so m∠JLK + m∠JLD = 180°. By the (substitution property of equality reflexive property of equality, or division property of equality) , m∠IKL + m∠JLD = 180°. Therefore, ∠IKL and ∠JLD are supplementary angles by definition.