At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga.
Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus.
Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
Do you mean she has a box of 20 cookies
Your question probably meant to read a "box of 20 cookies" not 2. She is LESS 2 cookies for each friend, so the slope is a negative 2 and the intercept is 20 because she started with that many. So, 20 - 2m after "m" friends is the # of cookies left.
I am guessing that was a typo and you meant that she had a box of 20 cookies. You said she gave 2 cookies to each friend, then that means that 2m, where m is the number of friends is the number of cookies that she gives away in total. So, to know how many she has left, you subtract 2m from the cookies she had in first place (20). Therefore, the expression would look like this:
That is choice B.