A flask has a mass of 78.23 g empty and 593.63 g when filled with water. when the same flask is filled with liquid x, its mass is 1026.57 g. what is the density of liquid x

So, they give the weight before and after. The density of water is 1g/cm^3. In order to find the space in cm^3 you have to see how many grams the water weighs ... 593.63-78.23 = 515.4 ... so there are 515.4cm^3. Now the formula for density is m/v. So you have the volume of the empty flask and the weight of liquid x. You do 1026.57g/515.4cm^3 ... And there you go: about 1.9914g/cm^3. (I rounded it)