An exterior angle is equal to the sum of the two opposite inside angles.
The picture shows an exterior angle of 115 degrees.
It's two opposite inside angles are the two equations.
This means:
(4k +5) + (6k+10) = 115
Combine like terms:
10k + 15 = 115
Subtract 15 from both sides:
10k = 100
Divide both sides by 10:
k = 100/10
k = 10