13. The area is 169π ft².
14. The circumference is 34π mm.
15. The circumference is 12 π in.
16. The area is 441π m².
Calculation of the area & circumference:
Since 
The circumference of a circle should be 
C = 2π*r
And, Area of a circle should be 
A = π*r²
Here, r is the radius of the circle
Now
13. 
Since the circumference of the circle is  26π ft
So, its radius is:
26π = 2π*r
r = 26π/(2π) = 13 ft
So, 
A = π*13² 
= 169π ft²
16. Since area of the circle is 289π mm²
So, its radius is:
289π = π*r²
r = √289
r = 17 mm
So, 
C = 2π*17 
= 34π mm
17. Since area of the circle is 113.1 in²
So, its radius is:
113.1 = π*r²
r = √(113.1/π)
r = 6 in
So, 
C = 2π*6 
=  12π in
18. Since circumference of the circle: 131.95 m
So, its radius is:
131.95 = 2π*r
r = 131.95/(2π)
r = 21 m
So, 
A = π*21² 
= 441π m²
learn more about the area here: https://brainly.com/question/17397308