Soybean meal is 18% protein, cornmeal is 9% protein. how many pounds of each should be mixed together to get a 360 pound mixture that is 15% protein ?

Question

Soybean meal is 18% protein, cornmeal is 9% protein. how many pounds of each should be mixed together to get a 360 pound mixture that is 15% protein ? 
Word problems are my favorites, but this one is confusing me. Help is very much appreciated

Damon · Answer

.18 s + .09 p = .15(s+p) and s+p=360

Christy · Answer

If I did this correctly it is 120 lbs cornmeal, 240 lbs soy