$\begin{align}   & \widehat{B}=65,\widehat{A}=90\Rightarrow \widehat{C}=180-\left( \overset{155}{\mathop{\not{90+65}}}\, \right)=25 \\  & \overset\frown{AB}=2\widehat{C}=2\left( 25 \right)=50 \\ \end{align}$