Discussion

Explanation:

Let us draw a line joining points C and A and extend it till E.

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In ∆ABC, ∠EAB is the exterior angle, hence
∠EAB = ∠ABC + ∠BCA   ...(1)

In ∆ADC, ∠EAD is the exterior angle, hence
∠EAD = ∠ADC + ∠DCA   ...(2)

(1) + (2)

∠EAB + ∠EAD = ∠ABC + ∠BCA + ∠ADC + ∠DCA
⇒​​​​​​​ ∠BAD = ∠ABC + ∠ADC + ∠BCD
⇒​​​​​​​ ∠BAD = 30° + 10° + 20° = 60°

Hence, option (d).

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