Cynthia made the conjecture that the sum of any prime number and any composite number is a composite number.
which equation is a counterexample to her conjecture?
a.
11 + 2 = 13
b.
5 + 8 = 13
c.
13 + 2 = 15
d.
11 + 9 = 20

Well,

We will need an equation in the form of:
(prime no.) + (composite no.) = (prime no.)

Options C and D immediately are rejected because the result is a composite number.

Option A looks like it could be a counterexample, but 2 is a prime number.

That leaves option B, which is the correct option.

Pretty much, all you have to do is 57.1 times 3600

you do that because there 3600 seconds in an hour

i hope that helps