Answer:
if everyone fills there cup wvenly it is 12 or
Step-by-step explanation:
1 cup = 8 ounces so there is 13 cups right ? so they have to fill it back up when htere is a cup left so 13 minus 1 cup of water is 12.
ANSWER IS 12 DUE TO THE FACT THAT IT HAS TO BE CHANGED WHEN THERE IS ONLY 1 CUP LEFT ( not yelling just want you to see and understand my answer sorry for the caps.)