$\widehat{xOz}=\frac{2}{3}\widehat{yOz}$
Mà $\widehat{xOz}+\widehat{yOz}=\widehat{xOz}=180^o$( hai góc kề bù)
$\Leftrightarrow 180^o-\widehat{yOz}=\widehat{xOz}$
$\Rightarrow \frac{2}{3}\widehat{yOz}=180^-\widehat{yOz}$
$\Leftrightarrow \frac{5}{3}\widehat{yOz}=180^o$
$\Leftrightarrow \widehat{yOz}=108^o$
$\Rightarrow \widehat{xOz}=180-108=72^o$
Vậy $\widehat{yOz}-\widehat{xOz}= 108^o-72^o=36^o$