Step-by-step explanation:
∆ADB and ∆CDB
has length AB = CB
DB _|_ AC
so length AD= CD
4=y
y=4
if ∆ADB=CDB
mBAD = mBCD
mBCD =52°
m∆CDB=180°
so x=m∆CDB-mBCD
x=180°-52°
x=128°
