If the Soda holds 51/2 Of a gallon of Soda you need to 51 by 2 which is 25.5
2
2[51
-4
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then add the 1
25
2[51
-4 2x5 equals 10
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11
- 10
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1 half of 2 is 1 half of 1 is 0.5 1 is your remainder 1 equals 0.5
25 + 0.5 equals 25.5 that's how many gallons you have. :)