[tex]\begin{gathered} \angle4=\angle1 \\ \angle1=140 \\ \angle3=180-140=40 \\ \angle3=\angle2 \\ \angle2=40 \\ \angle6=\angle4 \\ \angle6=140 \\ \angle7=\angle6 \\ \angle7=140 \\ \angle5=\angle3 \\ \angle5=40 \\ \angle8=\angle5 \\ \angle8=40 \end{gathered}[/tex]
