Step-by-step explanation:
Volume of intravenous solution to be delivered = 50 mL
1) Rate of drops per milliliter of the solution = r = 60 drops/mL
Number of drops delivered :

Time required to deliver 3000 drops = t
Rate of drop solution with respect to time = R = 1 drop/second

t = 3000 seconds = 50 minutes (1 min = 60 seconds)
Number of drops delivered 3000.
50 minutes are required to deliver 50 mL of intravenous solutions.
2) Rate of drops per milliliter of the solution = r = 15 drops/mL
Number of drops delivered :

Time required to deliver 750 drops = t
Rate of drop solution with respect to time = R = 1 drop/second

t = 750 seconds = 12.5 minutes (1 min = 60 seconds)
Number of drops delivered 750 .
12.5 minutes are required to deliver 50 mL of intravenous solutions.