+) \(\Rightarrow\widehat{yOt}=\widehat{xOy}-\widehat{tOx}\)
\(\widehat{yOt}=180^o-30^o\)
\(\widehat{yOt}=150^o\)
+) \(\Rightarrow\widehat{tOt'}=\widehat{xOy}-\left(\widehat{tOx}+\widehat{t'Oy}\right)\)
\(\widehat{tOt'}=180^o-\left(30^o+60^o\right)\)
\(\widehat{tOt'}=180^o-90^o\)
\(\widehat{tOt'}=90^o\)