The missing variables of the angles are:
a) a = 86
b) a = 108
b = 88
c = 90
c) x = 120
d) x = 127.5
How to find the angles in a quadrilateral?
a) Sum of angles in a quadrilateral is 360 degrees. Thus:
a + a + 16 + 2a = 360
4a + 16 = 360
4a = 344
a = 86
b) The sum of angles on a straight line is 180 degrees and as such:
a + 72 = 180
a = 108
Similarly:
b + 92 = 180
b = 88
Sum of angles in a quadrilateral is 360 degrees. Thus:
108 + 88 + 74 + c = 360
c + 270 = 360
c = 90
c) This is a six sided polygon and the sum of angles internally is 720 degrees. Thus:
x + x + x + 120 + 150 + 90 = 720
3x + 360 = 720
x = 360/3
x = 120
d) This is an eight sided polygon and the sum of angles internally is 1080 degrees. Thus:
x + x + x + x + x + x + 60 + 2x = 1080
8x = 1080 - 60
8x = 1020
x = 1020/8
x = 127.5