Angles 1 and 4 are alternate angles and thus have the same measurement. You will set their equations equal to each other and solve for the variable.
6n + 1 = 4n + 19
Subtract 1 and 4n from both sides to get variables on one side and constants on the other.
6n - 4n = 19 - 1
Combine like terms and solve for n.
2n = 18
n = 18 / 2
n = 9
Angles 1 and 2 are congruent as labeled in the graph.
So angle 2 is also 6n + 1
Plug in for 9 for n
6(9) + 1
54 + 1
55
Option C is your answer.
