a)  Ta thấy $yy' \perp MN$ và $zz' \perp MN$ => yy' // zz'

b) Ta có $\widehat{xAM}=\widehat{ABN} = 60^{\circ}$ (Đồng vị) 

$\widehat{ABz} +\widehat{ABN} = 180^{\circ}$ (kề bù)

=> $\widehat{ABz}$ = $180^{\circ}-\widehat{ABN}=180^{\circ}-60^{\circ} =120^{\circ}$

c)

Ta có yy' // zz' => $\widehat{ABz}=\widehat{BAM} = 120^{\circ}$ (so le trong)

$\widehat{HAM}=\widehat{HAB} = 120^{\circ}:2= 60^{\circ}$

$\widehat{HAM}=\widehat{AHB}= 60^{\circ}$ (so le trong)

$\widehat{AHB} +\widehat{AHN} = 180^{\circ}$ (kề bù)

=> $\widehat{AHN}= 180^{\circ}- 60^{\circ}=120^{\circ}$