Hey there mate :)
As per question,
Given that Nicole made:-
And she packed:-
1. The number of boxes can be obtained as the quotient when 5x^3-13x^2-20x+800 divided by x-5.
(The division part is attached as image. Check it)
Thus the number of boxes is 5x^2+12x+40
2) The number of cupcakes left unpacked is equal to the remainder when 5x^3-13x^2-20x+800 divided by x-5.
Thus, the number of cakes left and unpacked is 1000