The answer to your question is the last one through the method of competing the square
Answer:
Given - A rectangle of length 18 feet and wide 14 feet
To find - Area
Solution -
Area of rectangle = Length * Breadth
=

square feet
Janet = 1/3
Gary = 1/2
(1/3) + (1/2) = 5/6
Let x = time they both can do the job together
(1/2) + (5/6)x = 1
Solve for x to find your answer.