Răspuns :
[tex]\it Vom\ nota\ \widehat{AOC}=x,\ \widehat{COD}=x\\ \\ 2\cdot\widehat{DOB}=5x \Rightarrow \widehat{DOB}= \dfrac{5x}{2}\\ \\ \\ x+x+\dfrac{5x}{2}=180^o|_{\cdot2} \Rightarrow 2x+2x+5x=360^o \Rightarrow 9x=360^o|_{:9} \Rightarrow x=40^o\\ \\ \\ Deci,\ \ \widehat{COD}=40^o;\ \ \ \widehat{DOB}=\dfrac{5\cdot40^o}{2}=100^o[/tex]