In ΔADC
∠CAD+∠ADC+∠DCA=180∘ [Angle sum property]
⇒∠CAD+∠ADC+64∘=180∘
⇒∠CAD+∠ADC=(180∘−64∘)=116∘
But CD = CA ⇒∠CAD=∠ADC [ ∵ ∠s opposite to equal sides of a Δ are equal]
So, ∠CAD=∠ADC=116∘2=58∘
Now, ∠ADC=∠ABD+∠DAB
[Ext. ∠ of a Δ = sum of int. opp. ∠s]
But, AD=BD⇒∠ABD=∠DAB.
So, ∠ADC=2∠DAB
⇒∠DAB=12∠ADC
⇒x=12×58∘=29∘
Hence, x=29∘