Ta có:
\(\widehat{A}=3\cdot\widehat{C}\\ \widehat{B}=4\cdot\widehat{C}\\ \widehat{D}=2\cdot\widehat{C}\\ \Rightarrow\widehat{A}+\widehat{B}+\widehat{C}+\widehat{D}=3\cdot\widehat{C}+4\cdot\widehat{C}+\widehat{C}+2\cdot\widehat{C}\\ \Leftrightarrow10\cdot\widehat{C}=360^o\\ \Leftrightarrow\widehat{C}=36^o\\ \Rightarrow\widehat{A}=3\cdot\widehat{C}=3\cdot36=108^o\\ \widehat{B}=4\cdot\widehat{C}=4\cdot36^o=144^o\\ \widehat{D}=2\cdot\widehat{C}=2\cdot36^o=72^o\)
Vậy \(\widehat{A}=108^o;\widehat{B}=144^o;\widehat{C}=36^o;\widehat{D}=72^o\)