Answer:
85
Explanation:
The exterior angle is equal to the sum of the two interior opposite angles, therefore:
m<ACD = m<A + m<B
120 - x = 10 + x + 60
1) Solve for x:
120 - x = 10 + x + 60
120 - x = 70 + x
Add x on both sides to give:
120 = 70 + 2x
Subtract 70 on both sides:
50 = 2x
x = 50/2 = 25
2) substitute x = 25 to find the angle of m<ACD
m<ACD = 120 - x = 120 - 25 = 95
3) To find out m<ACD(y):
Angles on a straight line add up to 180, so add m<ACD and y and equate to 180 to solve for y
95 + y = 180
y = 180 - 95 = 85