Need help! I don’t get what I’m going wrong?

Determine the approximate value of side a.

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

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Quickly multiply and simplify polynomials (x – 4) (x^2 – 5x – 6)