Question
A stationery booth sells files in packs of 4 and 7. At first, there were 3 times as many packs of 4 as packs of 7. After selling half of the packs of 4 and some packs of 7, Mr Heng packs 6 additional packs of 7. How many packs of 4 are sold if there are 6 times as many packs of 4 as packs of 7 and there is a total of 310 unsold files?
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A stationery booth sells files in packs of 4 and 7. At first, there were 3 times as many packs of 4 as packs of 7. After selling half of the packs of 4 and some packs of 7, Mr Heng packs 6 additional packs of 7. How many packs of 4 are sold if there are 6 times as many packs of 4 as packs of 7 and there is a total of 310 unsold files?