Answer:
60cm^2
Step-by-step explanation:
We assume that is a circumscribing quadrilateral, rather than one that is circumscribed. It is also called a "tangential quadrilateral" and its area is ...
K = sr
where s is the semi-perimeter, the sum of opposite sides, and r is the radius of the incircle.
K = (12 cm) (5cm) = 60 cm²
_____
A quadrilateral can only be tangential if pairs of opposite sides add to the same length. Hence the given sum is the semiperimeter.
18.5 - 6 = 12.5 gallons empty
12.5 / 18.5 = 0.676
0.676 x 100 = 67.6%
Answer: 67.6%