∠BEC and ∠DEA are vertical angles, so they are congruent and their measures are equal 5x-25 = 7x-65 -2x = -40 x = 20° So m∠BEC = 5x-25 = 5(20)-25 = 100-25 = 75° and m∠DEA = 7x-65 = 7(20)-65 = 140-65 = 75° ∠BEC and ∠DEB form a linear pair so the sum of their measures is 180°, so m∠DEB = 180°-75° = 105° ∠AEC and ∠DEB are vertical angles, so they are cngruent and their measures are equal, so m∠DEB = 105° Edwin