Understand the terminology when making such calculations. Solutes are liquids that can be dissolved in another liquid (solvent). Use milliliters (or mL) to measure your quantities. V/v is always in the form of a percentage.
Choose a substance to work with. For instance, alcohol can be dissolved in water (solvent) to achieve a certain concentration. Suppose you want to determine the concentration and percent of alcohol when 10 mL of 100 percent alcohol is dissolved in 100 mL of water.
Calculate v/v by comparing the amount of solute to the substance's final volume. So you would calculate 10 / (100 + 10) = 10 / 110, or 0.09. To get the percent of alcohol, just multiply the final answer by 100. In this case, it comes out 9 percent alcohol.
Add another step if you're not using 100 percent alcohol. For example, instead of using 100 percent alcohol, suppose that you are using 95 percent alcohol. (This is another way of saying 95 parts alcohol and 5 parts water.) Say you want to dissolve 10 mL of 95 percent alcohol in 100 mL of water. First, calculate the amount of pure alcohol that will be in the final solution: 10 x 0.95 = 9.5 mL of pure alcohol. To get percentage of alcohol, calculate 9.5 / (100 + 10) ) x 100. The result is 8.6 percent alcohol for the final solution.