Question 1130451
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<pre>
Let n = "How many radios did she buy",  the value under the question.


From the condition, you have this equation


{{{576/(n-4)}}} - {{{576/n}}} = 12.    (*)


576n - 576*(n-4) = 12*n*(n-4)


576*4 = 12*n*(n-4)


n*(n-4) = {{{(576*4)/12}}} = 192.


<U>Answer</U>.  n= 16.


<U>Check</U>.  {{{576/(16-4)}}} - {{{576/16}}} = 12.   ! Correct !
</pre>

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