Giải thích các bước giải:
Vì Ot nằm giữa Ox, Oy
$\to \widehat{xOt}+\widehat{tOy}=\widehat{xOy}=130^o\to \widehat{xOt}=130^o-\widehat{yOt}$
Mà $\widehat{xOt}-\widehat{yOt}=30^o$
$\to130^o-\widehat{yOt}-\widehat{yOt}=30^o$
$\to130^o-2\widehat{yOt}=30^o$
$\to 2\widehat{yOt}=100^o$
$\to \widehat{yOt}=50^o\to \widehat{xOt}=130^o-50^o=80^o$