The 33 children ate a total of 33 * 10 = <<33*10=330>>330 apples.
There were 450 - 330 = <<450-330=120>>120 apples left for the adults to eat.
If every adult ate 3 of the 120 apples left, then there were 120 / 3 = <<120/3=40>>40 adults in the family.
#### 40