HELP: Quantitative Lab Unknown Solutions!!?

Hi, we're doing this thing in Chemistry where we have to discover what are solution is. The teacher told us that we have to discover what our solution is, but , even if you know what it is just by doing a physical property test you have to prove it into your analysis and give a calculation detail to prove that the substance you found is the actual substance by proving it quantitatively. First, I want to discover which chemical formula my unknown substance has , but I don't know which test can do in order to figure that out. Also, I want to use calculations to back up my findings. but the problem is I don't know how I can do so.