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:
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: