In
△ABC,
CA=CBThus, ∠CBA=∠CAB=50o ...(Isosceles triangle property)
In △ACD,
∠CDA=∠CAD=x ...(Isosceles triangle property)
Sum of angles = 180o
∴∠CDA+∠CAD+∠ADC=180
x+x+∠ADC=180
∠ADC=180−2x
Also, ∠ADC=∠CAB+∠CBA ...(Exterior angle property)
180−2x=50+50
2x=80
x=40∘