An opera house has 150 rows; each row has ten seats. The ticket costs $10 per show. How much did the opera house earn from one of the shows if 20% of the seats were not taken?
The opera house has 150 x 10 = 
<gadget id="calculator">150*10</gadget>
<output>1_500</output>
1500 seats.
There are 1500 x 20/100 = 
<gadget id="calculator">1500*20/100</gadget>
<output>300</output>
300 seats that were not taken.
The total number of seats taken was 1500 - 300 = 
<gadget id="calculator">1500-300</gadget>
<output>1_200</output>
1200.
Therefore, the opera house earned $10 x 1200 = $
<gadget id="calculator">10*1200</gadget>
<output>12_000</output>
12000 from one of the shows.

<result>12_000</result>