Question 326253
A merchant has coffee worth $60 a pound 
mix with 40 pounds of coffee worth $90 
can be sold for $80 a pound. 
..
let $60 coffee be x pounds
$90 coffee 40 pounds
Total $ 80 , 40+x pounds
..
60x+90*40=80(40+x)
60x +3600=80x+3200
20x=400
x= 20 pounds