A nurse must give 1.2 L of saline through a drip in 8.0 h…

Step 1. Volume and time. $1.2\ \text{L} = 1200\ \text{mL}$, and $8.0\ \text{h} = 480\ \text{min}$.

Step 2. Rate. $\dfrac{1200\ \text{mL}}{480\ \text{min}} = 2.5\ \text{mL/min}$.

Step 3. Drops. $\dfrac{2.5\ \text{mL/min}}{0.050\ \text{mL/drop}} = 50\ \text{drops/min}$.