Question 320204
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Let *[tex \Large x] represent the number of quarters.  Then, since there are 30 coins in all, there must be *[tex \Large 30\ -\ x] 50-cent pieces.  The purchase was $10.50, so the change from $20.00 must be $9.50 or 950 cents.


Quarters are worth 25 cents, so *[tex \Large x] quarters must be worth *[tex \Large 25x] cents.  Likewise, 50-cent pieces are worth...wait for it now...50 cents, so *[tex \Large 30\ -\ x] 50-cent pieces must be worth *[tex \Large 50(30\ -\ x)] cents.


And finally:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ 25x\ +\ 50(30\ -\ x)\ =\ 950]


Solve for  *[tex \Large x] to get the number of quarters.



John
*[tex \LARGE e^{i\pi} + 1 = 0]
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