Answer:
it's c
Explanation:
x represents boxes 13 is the cookies in it 13x means 13 times x(amount of boxes) (example: 2 boxes is 13 times 2 to get total number of boxes ) and minus 26 because 2 boxes is 13(2) x equals 2 to get 26 and she keeps 26 to herself (aka 2 box) so it's c