Where’s the graph? I will need it if I can help.
For this case we propose a rule of three. We assume that the excess water received was in one day. So:
cup ------> 100%
x ----------------------------> 25%
Where "x" represents excess water.

Thus, the excess water is
cups.
Then, in one day you receive in total:
cups of water.
Answer:
cups of water
Answer:
7-2x=22-3x
-2x=15-3x (minus 7 from both side)
x=15 ( plus 3x from both side)