Ta có:
\(\left\{{}\begin{matrix}\widehat{xOy}+\widehat{yOz}=\widehat{xOz}\\\widehat{xOz}+\widehat{zOt}=\widehat{xOt}\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}\widehat{yOz}=30^o-10^o=20^o\\\widehat{zOt}=80^o-30^o=50^o\end{matrix}\right.\)
Vậy..............
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