Linear pairs of angles:
It means that they add to 180º.
In this question:
mZEFG = 5n + 21
mZGFH =4n + 15
Since they are linear:
mZEFT + mZGFH = 180
5n + 21 + 4n + 15 = 180
9n + 36 = 180
9n = 180 - 36
9n = 144
n = 144/9
n = 16
Now we have n, so we can find the measures of both angles.
mZEFG = 5n + 21 = 5*16 + 21 = 80 + 21 = 101
mZGFH =4n + 15 = 4*16 + 15 = 64 + 15 = 79
Answer:
mZEFG = 101, mZGFH = 79