Two packs of basketball cards cost 2 x $3 = $<<2*3=6>>6.
Five decks of baseball cards cost 5 x $4= $<<5*4=20>>20.
Thus, the total cost of the cards was $6 + $20 = $<<6+20=26>>26.
Therefore, Olivia received change of $50 - $26 = $<<50-26=24>>24.
#### 24