Answer
d = 80 degrees
c = 84 degrees
a = 101 degrees
b = 67 degrees
Work Step by Step
1. solve for a:
angle with 100 degrees --> a circle circumference of 200 degrees
200 - 99 (given) is 101.
a is 101.
2. solve for b:
96-degree angle --> circle circumference of 192 degrees
add 192 to 101 (a); remaining circumference --> 67. (360 - 293 = 67)
b is 67.
3. solve for c:
Half of a + b will be c.
101 + 67 is 168; c --> 168 / 2 = 84
c = 84.
4. solve for d:
the sum of angles of a quadrilateral --> 360 degrees
100 + 96 + 84 + d = 360
d = 80
