Aperson wishes to mix coffee worth $9 per lb with coffee worth $3 per lbto get 240 lbsof a mixture worth $5 per lbhow many pounds of the $9 and the $3 coffees will be needed?

In order to get $5 per pound, you need a ratio of 1:2. One $9 for every two $3 will get you $5 per pound, since 9 + 3 + 3 is 15, divided by 3 pounds is $5. For 240 pounds, divide by three (since there is one $9 and two $3). This is 80 times the 3 pounds at $5.
Therefore, 1 × 80 is 80 pounds of $9 coffee, and 2 × 80 is 160 pounds if $3 coffee. which totals 240 pounds at $5 per pound.

Could you make it more clear?