Answer:
m<D = 26
Step-by-step explanation:
Exterior angles thm:
83 + 6x - 4 = 21x + 4
6x + 79 = 21x + 4
6x - 21x = 4 - 79
-15x = -75
x = 5
m<D:
6x - 4
6(5) - 4
30 - 4
26
