I am having a lot of trouble with the pharmacy calculations is there anyway that someone can explain it in dummy terms?

3. Ordered: ciprofloxacin 500 mg p.o. q12h
On hand: ciprofloxacin 250 mg tablets
Amount to administer: _______________

9. Ordered: Zyloprim 0.25g twice daily
On hand: Zyloprim 100 mg scored tablets
Amount to administer ________

These are the ones that I am having trouble with.