How many pounds of peanuts that cost $0.70 per pound and cashews that cost $0.90 per pound can be combined to make 300 pounds of a mixture that will sell $0.75 per pound?

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Answer 1 · 2015-09-18T00:37:12

I found:
#225 pounds# of peanuts;
#75pounds# of cashews.

Call the quantity of peanuts #p# and cashews #c# so you get:
#{(p+c=300),(0.7p+0.9c=0.75*300):}#

From the first you get:

#p=300-c#

substitute into the second:

#0.7(300-c)+0.9c=225#
#210-0.7c+0.9c=225#
#c=75pounds#
back into #p=300-c# you get:
#p=300-75=225pounds#