Giaỉ:
Theo giả thiết, ta có:
- Góc xOy kề bù với góc yOz:
=> \(\widehat{xOy}+\widehat{yOz}=180^o\)
=> \(\widehat{yOz}=\widehat{xOz}-\widehat{xOy}=180^o-50^o=130^o\)
- \(\widehat{xOm}=\widehat{mOy}=\dfrac{\widehat{xOy}}{2}=\dfrac{50}{2}=25^o\)
=> \(\widehat{mOz}=\widehat{mOy}+\widehat{yOz}=25^o+130^o=155^o\)
=> Chọn D