单选题
For senior class pictures, a photographer charges x dollars to make a negative, 
dollars for each of the first 20 prints, and 
dollars for each of the first 20 prints, and
【正确答案】
C
【答案解析】You are given that the cost of the negative is x dollars and that the cost of the first 20 prints is [*] dollars per print. You are also given that any number of prints over 20 is [*] dollars per print. The question stem indicates that $80 is the total charge to make a negative and 30 prints. You know that the first 20 prints will cost [*] dollars per print and the remaining 10 prints will cost [*] dollars per print. Set up an equation and solve for x, as follows:
[*]
[*]