Answer:
$1.20
Explanation:
We assume that Karen brought 1 3/4 gallons, or 7/4 gallons. James brought 2 gallons, or 8/4 gallons. So, together, they brought ...
7/4 + 8/4 = 15/4 gallons
Dividing that quantity evenly between them, each hiker gets ...
(1/3)(15/4) = 5/4 gallons
This means James contributes ... (8/4 -5/4) = 3/4 gallon to Lou, while Karen contributes (7/4 -5/4) = 2/4 gallon to Lou.
If the $2 Lou contributed is divided in proportion to the water received, then for each quart Lou received, he has effectively paid
$2/(5 quarts) = $0.40 per quart
Since James contributed 3 quarts, he should receive
(3 quarts)($0.40/quart) = $1.20