The concentration of a solution is determined by the amount of solute dissolved in a given amount of solvent. In this case, the solute is salt and the solvent is water. To calculate the concentration, we need to know the mass of salt dissolved in 50ml of water.

Assuming the density of water is 1 g/ml, the mass of 50ml of water is 50 g. If the solution contains 20ml of salt, the mass of salt can be calculated as follows:

Mass of salt = Volume of salt * Density of salt

Assuming the density of salt is 2.16 g/ml, the mass of 20ml of salt is:

Mass of salt = 20 ml * 2.16 g/ml = 43.2 g

Therefore, the concentration of the solution is:

Concentration = (Mass of solute / Mass of solvent) * 100

Concentration = (43.2 g / 50 g) * 100 = 86.4%

Since the concentration of the solution is greater than 50%, it is considered to be concentrated.