SOLUTION
The brain behind the Exterior Angle Theorem is that:
the sum of two interior angles is equal to the one exterior angle.
In this question, we have that : ( Z - 9 ) + Z = Z + 45
Z - 9 + Z = Z + 45
2 Z - 9 = Z + 45
collecting like terms, we have:
2 Z - Z = 45 + 9
Z = 54 degrees
CONCLUSION: The value of Z = 54 degrees
