Question 144385
Setup two equations

let s be the weight of soy and c be the weight of corn

{{{s + c = 320}}}
{{{0.16s + 0.08c = 0.09*320}}}

Now use your favorite method to solve. I will use elimination
{{{-0.08s - 0.08c =(-0.08)320}}}
{{{0.16s + 0.08c = 0.09*320}}}
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0.08s            = (0.01)320
s = 40

then c=280

Plug in and verify the answers are correct