Answer:
4(3) -(7) = 5
2(7) -3(3) = 5
Step-by-step explanation:
Fill the empty 3-gallon bucket 4 times and transfer the contents to the 7-gallon bucket. When the 7-gallon bucket is full, empty it. After the 4th time the 3-gallon bucket is emptied, the 7-gallon bucket will contain 5 gallons.
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Alternatively, fill the empty 7-gallon bucket twice and transfer the contents to the 3-gallon bucket. Each time the 3-gallon bucket is full, empty it. After the 3rd time the 3-gallon bucket is emptied, the 7-gallon bucket will contain 5 gallons.