GWD-1-32 数学请NN指点

pyrbbb

Q32:

For a convention, a hotel charges a daily room rate of $120 for 1 person and x dollars for each additional person.  What is the charge for each additional person?

[MSOffice1] (1)            The daily cost per person for 4 people sharing the cost of a room equally is $45.

(2)   The daily cost per person for 2 people sharing the cost of a room equally is $25 more than the corresponding cost for 4 people.

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 为什么D正确，

 

（2）怎么可以推出具有sufficent?

thanks

pyrbbb

thanks

Snazzy

1， （120+3x)/4=45
2,   (120+x)/2=25+(120+3x)/4