Question 758219
A merchant wants to mix peanuts worth $3 per pound with jelly beans worth $1.50 per pound to make 40 pounds of a mixture worth $2.10 per pound. How many pounds of each should he use? 
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let x=lbs of peanuts to mix.
let y=lbs of jelly beans to mix
x+y=40
y=(40-x)
..
3x+1.50y=40*2.10                                                
3x+1.5(40-x)=40*2.1
3x+60-1.5x=84
1.5x=24
x=16
y=40-x=24
lbs of peanuts to mix =16
lbs of jelly beans to mix=24