The opera house has 150 x 10 = <<150*10=1500>>1500 seats.
There are 1500 x 20/100 = <<1500*20/100=300>>300 seats that were not taken.
The total number of seats taken was 1500 - 300 = <<1500-300=1200>>1200.
Therefore, the opera house earned $10 x 1200 = $<<10*1200=12000>>12000 from one of the shows.
#### 12000