If 40% of the balls had holes in them and could not inflate, their number was 40/100*100= <<40/100*100=40>>40
The remaining balls that Nova could inflate were 100-40 = <<100-40=60>>60
While inflating, 20% of the good soccer balls were overinflated and exploded up, a total of 20/100*60 = <<20/100*60=12>>12
The number of soccer balls that inflated successfully and could be used is 60-12 = <<60-12=48>>48
#### 48