(1) Extend the segment DC so it intersects with line BA. Call the intersection F.
(2) Consider triangle BCF. In here, we are given m<ABC=24 deg. Since m<BCD = 90 deg, we known that m<BCF = 90 deg. Knowing two angles in the triangle BCF lets us determine the rhird angle m<BFC = 180-90-24 = 66 deg.
(3) Because of the fact that AB || DE and the fact that line DF intersects AB and DE, the angles <BFC and <CDE are congruent. Therefore m<CDE=66 deg.
