Respuesta :

The measure of the whole angle is 90 degree

so that:
m(BDC) + m(CDA) = 90

-3x + 20 - 2x + 55 = 90

solving for x:
-5x + 75 = 90
-5x = 90 - 75 = 15

x=-3

and therefore
m(BDC) = -3x + 20 = -3*-5 + 20 = 15 + 20 = 35 degree