Question 767262
You can imagine dilution according to factors.  The new total quantity of solution is 18 quarts.  The baking soda is diluted by 10/18, and the soap is diluted by 8/18.


Baking soda:  {{{4*(10/18)=4*(5/9)=20/9=highlight(2&2/9)}}} percent
Soap:  {{{45*(8/18)=45*(4/9)=highlight(20)}}} percent