#### Answer

Estimate: 20+9+5+20+9+5 = 68ft
Exact : 64 ft.

#### Work Step by Step

We need to find the perimeter, so we need to add the all boundaries.
Let's First Find Estimate:
18 (Round off to) 20
9 (Round off to) 9
5 (Round off to) 5
Perimeter = 20+9+5+20+9+5 = 68ft
Now Let's find Exact:
18+9+5+18+9+5 = 64 ft