What is 20-2 in this question

What is the length of bc ? enter your answer in the box.bc =

Tom wants to order tickets online so that he and three of his friends can go to a water park the cost of the tickets is 16.00 per person there is also a 2.50 one-time service fee for ordering tickets online write an expression in term of n that represents the cost for n ordering tickets online

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36