A farmer has several packages of fertilizer for his new grain crop. The old packages contain 60 pounds of
long-term-growth supplement and 50 pounds of weed killer. The new packages contain 65 pounds of
long-term-growth supplement and 45 pounds of weed killer. Using past experience, the farmer estimates that he
needs 1550 pounds of long-term-growth supplement and 1200 pounds of weed killer for the fields. How many old
packages of fertilizer and how many new packages of fertilizer should he use?