Aiguo = <<20=20>>20 shells
Vail = 20 - 5 = <<20-5=15>>15 shells
Stefan = 15 + 16 = <<15+16=31>>31 shells
Total = 20 + 15 + 31 = <<20+15+31=66>>66
The 3 children had 66 seashells altogether.
#### 66