Step 1: Angle C (also called angle ACB) has to be 40º, because all angles of a triangle must sum 180º
Step 2: Therefore EAD has to be also 40º (i.e. equal to ACB), because that's a property if AD and BC are parallel
Step 3: Finally, angle DEA must be 45º, because (again) all angles of a triangle must sum 180º
Solution D: 45º
Step 2: Therefore EAD has to be also 40º (i.e. equal to ACB), because that's a property if AD and BC are parallel
Step 3: Finally, angle DEA must be 45º, because (again) all angles of a triangle must sum 180º
Solution D: 45º