When two lines cross like this, sum of measures of opposite angles is 180. this means that: measure angle AEC + measure angle BED = 180 4x-40 + x+50 = 180 5x +10 = 180 5x = 170 x = 34 therefore: measure angle AEC = 4x-40 = 4(34)-40 = 96 measure angle BED = x+50 = 34+50 = 84