Answer
CD = 11 units
Step-by-step explanation
From the image, we can see that
CD = 2x - 9
DE = x - 9
CE = CD + DE
CE = 12
CE = CD + DE
CE = (2x - 9) + (x - 9)
12 = 2x - 9 + x - 9
12 = 3x - 18
We can rewrite this as
3x - 18 = 12
3x = 12 + 18
3x = 30
Divide both sides by 3
(3x/3) = (30/3)
x = 10
CD = 2x - 9 = 2(10) - 9 = 20 - 9 = 11 units
Hope this Helps!!!