The Owner of a Produce Store Wanted to Mix Peanuts

Short Answer

The owner of a produce store wanted to mix peanuts selling for $1 per pound, cashews selling for $8 per pound, and Brazil nuts selling for $8 per pound to get 70 pounds of a mixture that would sell for $5 per pound. She used 15 fewer pounds of cashews than peanuts. How many pounds of peanuts did she use?