SOLUTION: Lorena bought 10 packs of styrofoam cups for the graduation dance. a pack of fifty 12-oz cups costs $1.80 and apack of fifty 16-oz cups costs $2.40. Lorena paid a total of $21.60 e

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Let = the number of packs of 12 oz cups she bought
Let = the number of packs of 16 oz cups she bought
given:
(1)
(2)
Multiply both sides of (1) by 180 and subtract from (2)
(2)
(1)


and, since
(1)


She bought 4 packs of 12 oz cups and
6 packs of 16 oz cups
check answer:
(2)
(2)


OK