Final answer:
To find the measure of angle ACD, set up an equation using the given angles and solve for x. Then, substitute the value of x back into the equation to find the measure of angle ACD.
Step-by-step explanation:
To find the measure of angle ACD, we need to use the fact that the incenter of a triangle is equidistant from the three sides of the triangle. This means that AD = CD. We can set up an equation using the given angles as follows:
m∠ACD = m∠ACB - m∠ACD
x + 31 = 3x + 54 - x
31 = 2x + 54
2x = -23
x = -11.5
So, m∠ACD = -11.5 + 31 = 19.5°