What is the answer to the question-)

Note that two negatives = one positive

so: -(-13) = +13

Combine the two numbers

-11 + 13 = 13 - 11

13 - 11 =2

2 is your answer

hope this helps

you didn't post any answer choices, so its not 100% clear what your teacher is looking for

however, log(15/7) is equivalent to log(15) - log(7)

i'm using the rule log(x/y) = log(x) - log(y)