Type the correct answer in each box. Use numerals instead of words. If necessary, use / for the fraction bar(s). John hosts an art workshop on the weekends. He has an average of 14 students in each session and charges a fee of $12 per session. He estimates that for every $2 increase in the fee, the average number of students reduces by 1.

Complete the equation that models this scenario, where c(x) is the revenue generated and x is the number of $2 fee increases.

c(x) = _x2 + _x +_
fill in the blank