(17), the first folding, you can get that ABFE is square, so the angle BFE is 45 degrees; The second time, we can see that the straight line EG bisects the angular bed, and the angle BEA(45 degrees) = 135 degrees, so we can see that the angular bed = 135 degrees and the angle BEG = 67.5 degrees, so the angle FEG=67.5 degrees -45 degrees =22.5 degrees.

Question (18), because BC//DE, angle ADE= angle B=50 degrees, so angle A 1DE=50 degrees, so angle BDA 1= 180 degrees-angle A 1DE-