science project

Just let your horizontal axis show time in days, and the vertical can show either evaporative loss, or amount of solution remaining. Either a manual graph with three colored lines connecting data points, or a quick Excel graph should do it.

Sorry to hear about your teacher. He/she is either vastly overworked, or way overpaid.

You should have weighed each glass on a lab scale. Then you should have accurately mixed a known volume of each solution strength. Id have used something like a burette. Then place each solution into each glass (Making sure that you kmnow the weight of esch glass).
Then, over the week, Id weigh each glass of each solution and subtract the tare weight of the glass and that would leave you with the remaining volume. You will lern a secret about what happens as things evaporate
As roger said, record the weight on the Y axis and the time (Id use cumulative minutes rather than days--a day is 1440 minutes).

Then you can plot the change in weight.
Record the ambient temp and humidity if you can.

If you plot the graph logarithmically each log cycle will provide you with some information about the strength of solution.