Determine the values for the volume of the known solution, the molarity of the known solution and the volume of the unknown solution. These will be given to you in the problem. For example, you may be told that 30 mL of 2.0 molar (M) acid was used with 60 mL of an unknown solution.
Multiply the concentration of the known solution by the volume of the known solution. For example, you would multiply 30 mL by 2 M to get 60 mL*M.
Divide the result from Step 2 by the volume of the unknown solution to find the molarity of the unknown solution. Continuing the example, you would divide 60 mL*M by 60 mL to find the molarity of the unknown solution equals 1 M.