Question 1123162
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Let x = amount that each of Cameron's 2 friends had to start with.

The the amount which Cameron had at the start was 2x.


Let y = the price of a box of candy. 


First equation is


    2x - 3y = 7.50    (1)    (After buying 3 boxes of candy Cameron had $7.50 left over.)

Second equation is

    x - 4y = 1        (2)    (His 2 friends each bought 4 boxes of candy and had $1 left.)

 
So, you have the system of 2 equations


   2x - 3y = 7.50     (1)
    x - 4y = 1        (2)


From equation (2), express  x = 4y + 1 and substitute it into equation (1). You will get


   2*(4y + 1) - 3y = 7.50

    8y + 2 - 3y = 7.50

    5y = 7.50 - 2

    5y = 5.50

    y = {{{5.50/5}}} = 1.10.


<U>Answer</U>.  The price of one box of candy is/was $1.10.
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Solved.