Final answer:
To find how many acres can be planted per pound of seed, divide the total acres (3) by the pounds of seed (28), resulting in approximately 0.107 acres per pound.
Step-by-step explanation:
The question asks us to determine how many acres can be planted with one pound of seed, given that it takes 28 pounds of seed to plant a 3-acre field.
 To get this answer, we divide the total number of acres by the total pounds of seed used. 
Thus, we perform the calculation 3 acres ÷ 28 pounds to get the result.
Step-by-step calculation:
- Write down the amount of seed used and acres planted: 28 pounds for 3 acres.
 - Divide the acres by the pounds of seed: 3 acres ÷ 28 pounds.
 - Do the division to find the number of acres that can be planted per pound of seed.
 
The answer is approximately 0.107 acres per pound of seed.