Answer:
x = 52
m<ACD = 159
m<ACB = 21
Explanation:
1) Set up an equation.
2x + 55 = 3x + 3 (the two interior angles on the opposite of the triangle and the exterior angle are equal to the exterior angle)
2) Solve for x.
2x + 55 = 3x + 3
-x + 55 = 3
-x = -52
x = 52
3) Substitute 'x' into each angle required to find m<ACD and m<ACB.
m<ACD = 3(52) + 3
= 156 + 3
= 159
CHECK:
2(52) + 55 = 159
104 + 55 = 159
159 = 159
m<ACB + m<ACD = 180
m<ACB + 159 = 180
m<ACB = 21