We want to find L2 and L3 angles in the figure given.
Given that:
L1 = 103.4
L4 = 76.6
Notice that L3 and L4 are supplementary angles and L1 and L2 are also supplementary angles. When two angles are supplementary angles, their sum is always 180°.
So,
[tex]\begin{gathered} \angle1+\angle2=180 \\ 103.4+\angle2=180 \\ \angle2=180-103.4 \\ \angle2=76.6 \end{gathered}[/tex]
And,
[tex]\begin{gathered} \angle3+\angle4=180 \\ \angle3+76.6=180 \\ \angle3=180-76.6 \\ \angle3=103.4 \end{gathered}[/tex]
