James went to the store to return a defective $45 tape recorder for a refund. at the same time, he bought some batteries for $3 per package. if he received $33 dollars of his refund, how many packages of batteries did he buy?
a.
4
c.
2
b.
11
d.
15

Answer is 4 packages:

n:  number of packages of batteries

$45 = $3n + $33
$45 - $33 = $3n
$12 = $3n
$12/$3 = n
4 = n

He bought (a.) 4 packages of batteries. He returned the defective tape recorder for a store credit of $45 dollars. We know that he received $33 in refund, so the amount of money he spent on batteries is his store credit minus the refund ($45-$33), which is $12. Each package of batteries costs $3, so the amount of packages he bought can be found by dividing the money he spent by the cost per package, or $12/$3, which is equal to 4 packages. 

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