The answer to this question is 8.86666666667
Each small doll cost 6.5 dollars and each large doll cost 10 dollars
x² - 20x + 91
x -13
x -7
your answer is (x - 13) (x - 7)
hope this helps
(1) will write us of the following form

(2) [do not it need explanation]

(3) Left place variable "y" and right place, variable "x" like this

(4) Integrate both members

(5) Solve us the integrals

(6) Isolate variable "y"

C: any cosntant