Answer:
x = 40
Step-by-step explanation:
∠D = ∠ADB + ∠BDC
= 30 + 40
= 70°
In ΔBDC,
BD = CD
∠DBC = ∠DCB {angles opposite to equal sides are equal}
∠DBC + ∠DCB + ∠BDC = 180 {Angle sum property}
2∠DCB + 40 = 180
2∠DCB = 180 -40
2∠DCB = 140
∠DCB= 140/2
∠DCB = 70°
In ΔADC,
x + ∠D + ∠C = 180
x + 70 + 70 = 180
x + 140 = 180
x = 180 - 140
x = 40°
