Remember that:
The angles 3 and 4 are supplementary angles.
The angles 1 and 2 are also supplementary angles.
When two angles are supplementary, their sum is always 180°, so, we could write:
[tex]\begin{gathered} \angle3+\angle4=180 \\ 93.4+\angle4=180 \\ \angle4=180-93.4 \\ \angle4=86.6 \end{gathered}[/tex]
And,
[tex]\begin{gathered} \angle1+\angle2=180 \\ \angle1+86.6=180 \\ \angle1=180-86.6 \\ \angle1=93.4 \end{gathered}[/tex]
