A composite number is one that can be made by multiply two numbers to each other. Since 49=7*7, 49 is a composite number.
Check:
You can check a multiplication chart, but you will see that 49 is the only one that can be multiplied by 2 numbers
Using the cosine double angle formula,

(Note I took the positive case since
terminates in the first quadrant)
Using the Pythagorean identity,

(Note I took the positive case since
terminates in the first quadrant)
8 out of 24 = 1 out of 3
5 out of 20 = 1 out of 4
1/3 is larger that 1/4
Jessica has the largest ratio