3 gallons 80% solution + 1 gallon 20% solution =

4 gallons with 65% soultion

Step-by-step explanation:

1. add the number of gallons together to find the total amount of the liquid in this case 4 gal.

2. Find the amount of solution in each part. In this case from the 3 gal there is 2.4 solution and for the 1 gal its 0.2 solution. I found this by finding the percentage.

3. Next, add the amounts of solution together to get 2.6 solution in all.

4. lastly, caluculate how much percent 2.6 is out of the total 4 gals. When you do this in all you get 4 gal with a 65% solution.