Angle FEG = 90 degrees based on the square marker symbol in the diagram.
Angle ABE = 90 degrees as well because BEF is 90 (supplementary to FEG) and because ABE and BEF are alternate interior angles
Angle D is 40 degrees. Why? because triangle DEG is a reflection of triangle FEG (this can be proven using SAS)
Angle EGF is 50 degrees. With any right triangle, the acute angles add to 90, so 40+50 = 90, or put another way 90-40 = 50
