Question 1161481
Assuming you omitted the work "no" in the description, for "(containing NO salt)", the description and question is for a simple dilutions.
Also, assuming "FLUID OUNCES" for volume; not "ounces".


x, how much water to add
140-x, amount of the 20% salt solution to add


{{{(0.2(140-x))/140=0.15}}}


{{{140-x=0.15*140/0.2}}}


{{{highlight(140-x=highlight(105))}}}-----------------the volume of the 20% salt solution to use.  This means {{{highlight(x=35)}}} fluid ounces of JUST WATER WITHOUT SALT TO ADD.



The variables could have been assigned the other way around.