Question 1149995
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Let x be the cost of one CD player and y be the cost of one portable radio.


Then from the condition you have this system of 2 equations

    25x + 20y = 1692.50    (1)    (total cost)

      x -   y =   20       (2)


To solve it, multiply equation (2) by 20;  keep equation (2) as is.  Then you have

    25x + 20y = 1692.50    (1')  

    20x - 20y =  400      (2')


Next, add equations (1') and (2').  Then the terms "20y" will cancel each other, and you will get a single equation for x

    25x + 20x = 1692.50 + 400

    45x       = 2092.50

      x       = {{{2092.50/45}}} = 46.50.


<U>ANSWER</U>.  $46.50 for one CD player and 46.50 - 20 = 26.50 dollars for one portable radio.


<U>CHECK</U>.  46.50*25 + 26.50*20 = 1692.50  dollars.    ! Precisely correct ! !
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Solved.