Every dilution problem is based on the same principle: whatever is put in the solution, stays there. This is just a mass conservation. If you know final concentration and final volume, you can easily calculate amount of substance needed, this will let you calculate volume of the solution that is source of the substance.

Looking for special "formulas" almost never works. What works is understanding the logic behind, this can help solve any problem, not only the ones you have been shown previously.