The Owner of a Home Decorating Shop Wants to Mix

Short Answer

The owner of a home decorating shop wants to mix dried rose petals selling for $7 per pound, dried lavender selling for $4 per pound, and buckwheat hulls selling for $2 per pound to get 20 pounds of a mixture that would sell for $4.40 per pound. She wants to use twice as many pounds of rose petals as lavender. How many pounds of each should she use?
__________ lb of rose petals, __________ lb of lavender, __________ lb of buckwheat hulls