$xx'//yy'$
$⇒\widehat{zAx}=\widehat{ABy}=50^o$ (đồng vị)
$⇒\widehat{ABy}+\widehat{xAB}=180^o$ (trong cùng phía bù nhau)
mà $\widehat{ABy}=50^o$
$⇒\widehat{xAB}=180^o-50^o=130^o$
hay $\widehat{BAx}=130^o$
Vậy $\widehat{ABy}=50^o$, $\widehat{xAB}$ hay $\widehat{BAx}=130^o$