How many pounds of nuts selling for $9 per lb and raisins selling for $3 per lb should a person combine to obtain 60 lb of a trail mix selling for $5 per lb

Let n be the number of lbs of nuts.

Let r be the number of lbs of raisins.

9n + 3r = 60 * 5 = 300 ... (1)

n + r = 60

n = 60 - r ... (2)

Plugging the expression for n in (2) into (1) we get:

9 (60 - r) + 3r = 300

which expands to:

540 - 9r + 3r = 300 ... (3)

Simplifying and rearranging (3) we get:

-6r = - 240

Therefore r, the weight of raisins = 40 lbs

and the weight of nuts is 60 - 40 = 20 lbs