Math pls help look at pic

Which value of c would make he following expression completely factored? 8x+cy

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

Mrs. gehrke said cheddar weighs 16.8 pounds. he actually weighs 15.2 pounds. what is the percent error?