For all dilution problems use the dilution equation: <span>C1V1 = C2V2 </span> <span>20*V1 = 6*55 </span> <span>V1 = 6*55/20 </span> <span>V1 = 16.5 gallons </span> <span>The final volume must be 16.5 gallons </span> <span>You must add 16.5 - 6 = 10.5 gallons water to be added. </span> Have a nice day