Question 318004
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)