Helen uses 3/4 cup of oil and 1/3 cup of vinegar to make salad dressing which is closest to how many times 3/4 is as great as 1/3

One of those figures is wrong.

apothem = side length / 2*tan(180/5)
apothem = 14 / 2 * tan (36)
apothem = 14 / 2 * 0.72654
apothem = 14 / 1.45308
apothem = 9.6347069673

Here is the formula you will need when you have those numbers correct.
Pentagon Area = 5 * side length * apothem / 2

Source:
http://www.1728.org/polygon.htm