If have 6 liters of gas in a piston at a pressure of 3 atm and compress the gas until its volume is 3 what will the new pressure inside the piston be?

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.