Let "e" represent the number of pounds of "expensive" seed (80ยข/lb). The total cost of the seed can be written as

(30-e)(.50) + (e)(.80) = 30(.75)

30(.50) + e(.30) = 30(.75)

e(.30) = 30(.75 - .50)

e = 25

25 pounds of the "expensive" seed should be used, along with 5 pounds of the "cheap" seed.

(30-e)(.50) + (e)(.80) = 30(.75)

30(.50) + e(.30) = 30(.75)

e(.30) = 30(.75 - .50)

e = 25

25 pounds of the "expensive" seed should be used, along with 5 pounds of the "cheap" seed.