SOLUTION: I am stuck on this stinking problem, I am unsure how they get 28 for the answer after adding the sum and multiplying by 10% Can anyone please help me out... The original question

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Question 318004: I am stuck on this stinking problem, I am unsure how they get 28 for the answer after adding the sum and multiplying by 10% Can anyone please help me out...
The original question is this
soybean meal is 14% protien, cornmeal is 7% protien, how many pounds of each should be mixed together in order to get 280 lb mixture that is 10 % protien?
Let x= cornmeal and y= soy bean meal....

0.07x+0.14y=28

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = the number of lbs of 14%-protein soybean meal, then (280-x) the number of lbs of 7%-protein cornmeal. When added together, these are to produce 280 lbs of 10-protein mixture.
0.14x+0.07(280-x) = 0.1(280)
0.14x+19.6-0.07x = 28
0.07x+19.6 = 28
0.07x = 8.4
x = 120 lbs of soybean meal.
280-x = 280-120 = 160 lbs of cornmeal.
Check:
0.14(120)+0.07(160) =16.8+11.2 = 28 = 0.1(280)