The process of dilution is one in which additional solvent is added to a solution. The amount of solute does not change. Molarity is a unit used to describe the concentration and equal moles of solute / L ov solution. When we dilute a solution, only the volume of solution increases so the molarity decreases. The formula we use for dilutions is
M1*V1 = M2*V2
where M1 and M2 are the concentrations of the original and dilute solutions, respectively and V1 and V2 are the corresponding volumes.
Since we want to make 25.00 mL of our dilute solutions, we know V2. We know the concentration of the original solution, M1 and the concentration of the diluted solution, M2. Therefore, we are solving for M1. We don't have to change the volumes to liters as long as the volumes are in the *same* units.
0.300 M (V1) = 0.100 M (25.00 mL)
V1 = 8.33 mL
Therefore, we need to take 8.33 mL of the 0.300 M solution and add it to a 25.00 mL volumetric flask. We need to add additional water up to the 25.00 mL mark so that we have exactly 25.00 mL of solution. The resulting solution will be 0.100 M. The same process will apply for the other two concentrations. We will just have different values for V1.