Question 289790
Say that f = number of floor tickets sold and b = number of balcony tickets sold.
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The total amount of tickets sold is 325, which means that <b>b + f = 325</b>
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The total amount collected is $10000, which means that the amount of tickets sold multiplied by the amount it costs would be 25b + 40f = 10000, which can be simplified by a division of 5 to: <b>5b + 8f = 2000</b>

The first equation can be multiplied by five, and the rest is just a matter of simple substitution:

5b + 8f = 2000 <- second equation
5b + 5f = 1625 <- first equation
______________ -
 0 + 3f = 375

Since 3f = 375, <b>f = 125</b>

The amount of balcony tickets sold (b) can be determined from b + f = 325, which means that b = 325 - f = 325 - 125, and <b>b = 200</b>