posted by billy .
You need 3.0-L of 0.13 M salt solution. All you can find is 0.40 M salt solution. How much of that solution will you need in order to make your desired solution (in liters)?
You dilute 0.4 M salt to 0.13 M , this is a dilution factor of 3.077. Thus, to make 3 L of final solution, you need 3L/3.077 = 974 ml or 0.974 L