The answer to this question is c
He made 3.75 gallons. There was 1/10 remaining, meaning each tenth was 6 cups. The entire thing is 10 tenths so you do 6(10) to get 60 cups. After converting to gallons by doing 60÷26, you get 3.75.
To determine the amount of water in the first 8 beakers, you will subtract the 19 ml that are in the 9th beaker from the total to see how much water was actually put into the first 8 beakers.
91 ml - 19 ml = 72 ml.
The 72 ml are divided evenly between 8 beakers.
72/8 = 9 ml
There would be 9 ml of water in each of the first 8 beakers.