Question 826416
The water by itself does not add any washing solution.  Zero percent washing solution.

See in my profile for the lesson Mixture: two concentrations, but in this example, {{{M=2+w}}}, in which w is how much water to add, and M, not really needed, is the final amount of total mixture.


{{{2*50/(w+2)=20}}} is all you need.  Note that the expression {{{w*0=0}}}, would not be necessary as part of the numerator.  You could use it, but absolutely not necessary.