The solution to 5 x1 will be what kind of number

Given the box plot, will the mean or the median provide a better description of the center? box plot with min at 10.5, q1 at 11.5, median at 12.5, q3 at 13.5, max at 15

Ineed someone to me answer my question i have to have this done and knocked out

Two florida panthers were weighed. one weighs 6x+21 pounds and the two together weigh 14x+11 pounds how much does he other panther weigh alone