Question

what is answer for it

Answer 1

ABC+CBA+ACB=180. (interior angle of a triangle and CBA is 90°)
40°+90°+ACB=180°
ACB=180°-130°
ACB=50°
ACB=DCE. (vertically opposite angle)

DCE+CDE+DEC=180°. (interior angles)
50°+75°+DEC=180°
125°+DEC=180°
DEC=180°-125°
DEC=55°