You have the following expression:
(2z - 3) + (5z - 6) = 180
in order to solvet the previous expression for z, proceed as follow:
(2z - 3) + (5z - 6) = 180 cancel out parenthesis
2z - 3 + 5z - 6 = 180 simplify like terms left side
7z - 9 = 180 add 9 both sides
7z = 180 + 9
7z = 189 divide by 7 both sides
z = 189/7
z = 27
Hence, the value of z is 27
Next, replace the values of z into the expression for the measureof angle M:
Hence, the measure of angle M is 129°
