急~要考試了 PREP-PS-2-62

2-62.

 In a certain furniture store, each week Nancy earns a salary of $240 plus 5 percent of the amount of her total sales that exceeds $800 for the week. 
                If Nancy earned a total of $450 one week, what were her total sales that week?

(A) $2,200

(B) $3,450

(C) $4,200

(D) $4,250

(E) $5,000

答案是5000 ，想請問

1.黃色畫線部份的意思是說，sales有超過800才有5%的費用嗎?

2.解答是說設total sales 為X元, 則 240+(x-800) 0.05=450

  但為什麼不可以直接設240+0.05X=450 ?

感激參與討論的所有NN們 

汗,看这个帖前1分钟正在做这道题.......

如果直接设成240+0.05X=450就不是超过800的部分的5%而是全部的5%了

plus 5 percent of the amount of her total sales that exceeds $800 for the week

注意语法，exceeds修饰amount，所以不是总数的5%