Các bạn giúp mình với

Hình 1.

a/ Ta có: $\widehat{BAx}=\widehat{ABy}=140^\circ$

mà 2 góc ở vị trí so le trong

$→Ax//By$

b/ $By//Cz$

$→\widehat{CBy}=\widehat{BCz}=150^\circ$ (hai góc so le trong)

Ta có: $\widehat{CBy}+\widehat{ABy}+\widehat{ABC}=360^\circ$

hay $150^\circ+140^\circ+\widehat{ABC}=360^\circ$

$↔290^\circ+\widehat{ABC}=360^\circ$

$↔\widehat{ABC}=70^\circ$

Vậy $\widehat{ABC}=70^\circ$ thì $By//Cz$

Hình 2.

$By//Ax$

$→\widehat{xAB}+\widehat{ABy}=180^\circ$ (2 góc trong cùng phía)

hay $\widehat{xAB}+150^\circ=180^\circ$

$↔\widehat{xAB}=30^\circ$

Ta có: $By//Ax,By//Cz$

$→Ax//Cz$

$→\widehat{xAC}=\widehat{ACz}$ (2 góc so le trong)

hay $\widehat{xAB}=\widehat{BCz}$

$↔30^\circ=\widehat{BCz}$

Vậy $\widehat{xAB}=\widehat{BCz}=30^\circ$ thì $By//Ax,By//Cz$