By approximately what percent did the ratio of royalties to sales decrease from the first $20 million in sales to the next $108 million in sales? 版税的百分比从第一个到第二个下降了多少. 用(3/20-9/108)/(3/20) 就是,计算比较复杂,通过这个计算会简单些,先求两个版税之间的比例. R1:R2=(3/20)/(9/108)=18:10 再求答案 R1-R2)/R1=(18-10)/18=4/9=44.444% | 
