SOLUTION: In a quadrilateral ABCD,angle DAB=60 degrees and the other three angles are equal. The line CE is drawn parallel to BA to meet AD at E. calculate the angles ABC and ECD.

The sum of the four internal angles of a quadrilateral is 360°.
Since ∠A is 60°, that leaves 300° for the sum of angles
∠A, ∠BCD, and ∠D.  Therefore they are 100° each since they are equal.



∠A and ∠CED are equal since they are corresponding angles when 
transversal AD cuts parallel lines AB and CE, and so ∠CED = 60°.



The three interior angles of ᐃECD must have sum 180°, and
since ∠CED = 60° and ∠D = 100°, they sum to 160°, leaving
∠ECD = 20°

Edwin