[讨论]天山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.

key：A   

mine：c

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

会不会有Sales August<2000的情况呢

这样那两个式子就不成立

是道争议题，看讨论

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