Ta có: $\widehat{A}+\widehat{B}+\widehat{C}=180^{\circ}$ nên $105^{\circ}+(180^{\circ}-8x)+x=180^{\circ}$.
Suy ra $x=15^{\circ}$.
Ta có: $\widehat{A}+\widehat{B}+\widehat{C}=180^{\circ}$ nên $105^{\circ}+(180^{\circ}-8x)+x=180^{\circ}$.
Suy ra $x=15^{\circ}$.