Question 757645
Let a = the number of lbs of the $9/lb coffee
Since there are 20 lbs in the mixture, the number of lbs of the $6/lb coffee will be 20 - a
Adding up the total dollar amount of the two coffees and equating that to the total in the mixture gives
9a + 6(20-a) = 7.80*20
Solve for a:
9a + 120 - 6a = 156
3a = 36
a = 12
So there are 12 lbs of the $9 coffee and 8 lbs of the $6 coffee