3-6

Sue’s monthly earnings consist of a monthly salary and a 4 percent commission on the portion of her monthly sales that is in excess of $2,000. If Sue’s monthly salary was the same in July as in August, how much greater were her sales in July than in August? (1) Sue’s monthly earnings were $3,620 in July and $3,580 in August. (2) Sue’s monthly salary was $3,500 in July and in August.

sales that is in excess of $2,000. 意思是超过2000的部分拿4%佣金

key：A

mine：c

（1）（2）相减的两个月4%sales的差，再除4%就好了

大家说呢？

你的理解是对的，但是（1）可以得到两个方程：

3620=Salary July+4%(Sales July -2000) a

3580=Salary August+4%(Sales August-2000) b

Salary July=Salary August

a-b可以得到Sales July - Sales August的值

我选择A

PS:不要先同时看条件1和条件2，应该一个一个看，如果1满足，答案必然是A,D！（作DS的方法）