hình :
ta có : \(\widehat{xOt}+\widehat{yOt}=180^o\)( kề bù )
=> \(3\left(\widehat{xOy}+\widehat{yOt}\right)=3\left(180^o\right)\Rightarrow3\widehat{xOy}+3\widehat{yOt}=540^o\)
thay số ; \(3\widehat{xOt}=2\widehat{tOy}\)
=>\(2\widehat{tOy}+3\widehat{tOy}=540^o\Rightarrow5\widehat{tOy}=540^o\Rightarrow\widehat{tOy}=108^o\)
thay \(\widehat{tOy}=108^o\)vào bt \(\widehat{xOt}+\widehat{yOt}=180^o\)ta có :
\(\widehat{xOt}+108^o=180^o\Rightarrow\widehat{xOt}=72^o\)