concentration of solution is 20%
Mass of solute( common salt) is 80g
take the amount of water as x
mass of the solvent = (80+x)
We know, concentration of solution = (mass of solute/mass of solution)×100
20=(80/80+x)×100
80+x=80×5 ( we devide the both side by 20)
x= 400-80
x=320 g
