The solubility of sodium chloride in water tells you how many grams of sodium chloride can be added per
You know that at
Since a solution is a homogenous mixture, i.e. it has the same composition throughout, you can use the solubility of the salt at this temperature as a conversion factor to determine how many grams of water would be needed to make a saturated solution of sodium chloride that contains
#66.5 color(red)(cancel(color(black)("g NaCl"))) * overbrace(("100. g H"_2"O")/(36.0color(red)(cancel(color(black)("g NaCl")))))^(color(blue)("the solubility of the salt at 20"^@"C")) = color(darkgreen)(ul(color(black)("185 g H"_2"O")))#
The answer is rounded to three sig figs, the number of sig figs you have for your values.
You can thus say that at