Answer:
C₁ = 47 feet
C₂ = 28 feet
C₃ = 113 feet
Step-by-step explanation:
First, remenber that the circunference (or circunference lenght) can be calculated as follows:

Now, let's calculate the circunferences for each circle:
Circle 1:
Radius (r) = 7.5 feet
C₁ = 2πr
C₁ = 2π*7.5
C₁ = 15π
Considering π = 3.14
C₁ = 15*3.14
C₁ = 47 feet
Circle 2
Diameter (D) = 9 feet
C₂ = πD
C₂ = 9π
Considering π = 3.14
C₂ = 9*3.14
C₂ = 28 feet
Circle 3
Radius = 18
C₃ = 2πr
C₃ = 2π*18
C₃ = 36π
Considering π = 3.14
C₃ = 113 feet