问两道数学题

Lycoris7428UID: 3117631

1.A car dealer who gives a customer a 20 percent discont on the list price of a car still realized a net profit of 25 percent of cost. If the dealer's cost is $4800,what is the usual list price of the car?
A $6000   B $6180 C $7200 D $7500 E $8001

答案是D，但我不清楚题目中cost指代的是什么，所以没有选对


2.Exactly three years before the year in which Anna was born,the year was 1980+X. In terms of X,on Anna's twentieth birthday the year will be
A 1977+X   B 1997+X C 2003-X D 2003+X E 2006+X

答案是C，做题时没弄清1980+X指的是那年

希望各位帮忙解答下，谢谢

Astridcai90UID: 3132551

1. 设list price为x,
(1-20%)*x=(1+25%)*4800 得到x=7500
这里的cost就是我们一般理解上的没有利润的那个价格

Lycoris7428UID: 3117631

啊，原来是这样，谢谢。