To calculate the concentration of a solution, you can use the formula:
Concentration (in g/mL) = Mass of solute (in g) / Volume of solution (in mL)
Given that the solution contains 75g of sodium chloride (NaCl) and the volume of the solution is 300ml, you can plug in these values to calculate the concentration:
Concentration = 75g / 300ml
Concentration = 0.25 g/mL
So, the concentration of the sodium chloride solution is 0.25 g/mL.