My Teacher didn't teach us this please help

The osmotic pressure exerted by a solution is equal to the molarity multiplied by the absolute temperature and the gas constant r. suppose the osmotic pressure of a certain solution is measured to be 12.atm at an absolute temperature of 317k. write an equation that will let you calculate the molarity c of this solution. your equation should contain only symbols. be sure you define each symbol other than r. equation: c=? definition of symbols: ? = 12 atm ? = 317 k