Answer:
Θ=15
Step-by-step explanation:
AD=DC so triangle BCD is isosceles, so angle DBC = angle BCD = Θ
So angle BDC=180-Θ-Θ=180-2Θ
angle BDE = 180- angle BDC = 180-180+2Θ=2Θ
in triangle BDE all angles must add up to 180
angle BED= 180- angle BEA=180-90=90
so
90+4Θ+2Θ=180
90=6Θ
Θ=15
