Answer:
[tex]\large \boxed{28}[/tex]
Step-by-step explanation:
1. Calculate the number of cups
[tex]\text{Cups} = \text{12 lb}\times\dfrac{1\frac{3}{4} \text{ cups}}{\text{1 lb}} =12\times\dfrac{\text{7 cups}}{4} = 3\times7\text{ cups}= \text{21 cups}[/tex]
2. Calculate the number of bird feeders
[tex]\text{ Feeders}= \text{21 cups} \times \dfrac{\text{1 feeder}}{\frac{3}{4}\text{ cup}}=\text{21 cups} \times \dfrac{\text{4 feeders}}{\text{3 cups}} = 7 \times \text{ 4 feeders}\\\\= \textbf{28 feeders}\\\text{The volunteer can fill $\large \boxed{\textbf{28 feeders}}$}[/tex]