Question 420443
Let x=amount of soybean meal needed
Then 280-x=amount of cornmeal needed

Now we know that the amount of pure protein that exists before the mixture has to be equal to the amount of pure protein after the mixture, so:

Pure protein before the mixture:
0.14x+0.07(280-x)

Pure protein after the mixture:
0.08*280

Our equation to solve is:
0.14x+0.07(280-x)=0.08*280 simplify
0.14x+19.6-0.07x=22.4 subtract 19.6 from each side and collect like terms
0.07x=2.8
x=40lb---------amount of soybean meal needed
280-x=280-40=240lb-------amount of cornmeal needed

CK
40*0.14+240*0.07=280*0.08
5.6+16.8=22.4
22.4=22.4

Hope this helps---ptaylor