The triangles are isosceles. The following notation are for the angles. For example ABD is refer to the angle located in the B vertex, formed by the segments AB and BD.
[tex]ABD = ADB\\40 + 2ADB = 180\\ADB = 70 = ABD\\[/tex]
[tex]70 + DBC + 30 = 180\\DBC = 180 - 100 = 80[/tex]
Then
[tex]BCD = BCD\\2BCD + 80 = 180\\BCD = 50[/tex]
