In the first row, there are now 24 – 3 = <<24-3=21>>21 people.
In the second row, there are now 20 – 5 = <<20-5=15>>15 people.
So in total there are 21 in the first row + 15 in the second row + 18 in the third row = <<21+15+18=54>>54 people.
#### 54