7 2/15 plus 5 2/3 plus 9 13/15 ? Plz help

An equation of the line tangent to y=x^3+3x^2+2 at its point of inflection is

Elena is paid a constant rate for each hour she works. the table shows the amounts of money that elena earned for various amounts of time that she worked.

When solving this problem: 3025/5.5 = a/90.75 you get 49912.5 which would be the length of one of the sides of a square when the area is only 90.75 inches. is that answer correct, why, and how is it possible?