一道折磨我的题,求救!谢谢!!

pychina

For a recent play performance, the ticket prices were $25 per adult and $15 per child.  A total of 500 tickets were sold for the performance.  How many of the tickets sold were for adults?
(1)     Revenue from ticket sales for this performance totaled $10,500.
(2)     The average (arithmetic mean) price per ticket sold was $21.
我选的是E,而答案是D,请问是不是答案错了?

东岸老男人

同学，这是个2元一次方程啊，假设成人一共卖a张，小孩卖了c张

从第一个条件可以知道

25a+15c=10500

a+c=500

这个方程你会解吧？

从第二个条件可知道：

a+c=500

（25a+15c)=21X500

这个方程你会解吧？

所以是都单独可以。

你一定是看漏了条件。：）

pychina

晕,老大,神人啊,我确实漏看了!结果选的是C~非常感谢

pychina

晕,老大,神人啊,我确实漏看了!结果选的是C~非常感谢

sunnyblue13s

答案應該是D吧~~

X+Y=500

1.)25X+15Y=10500

2.)21*500=10500

只要補足其中一項皆可~~  答案應該是D囉~~