To solve this question we will use the following diagram as reference:
Notice that angles 1 and 2 are consecutive exterior angles, therefore they must add up to 180 degrees, meaning:
[tex]\measuredangle1+\measuredangle2=180^{\circ}.[/tex]
We know that ∠1 measures 77°, therefore:
[tex]77^{\circ}+\measuredangle2=180^{\circ}\text{.}[/tex]
Subtracting 77° from the above equation we get:
