The first week he spends: $12 * 1/3 = $<<12*1/3=4>>4.
So he has $12 - $4 = $<<12-4=8>>8 left.
In the second week, he spends $8 x 1/4 = $<<8*1/4=2>>2.
So Tom has $8 - $2 = $<<8-2=6>>6 left to finish the month.
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