Question 1023988
v gallons of the 20% acid and 100-v gallons of the 12% acid.  Concentration wanted is 18%.


{{{(12(100-v)+20v)/100=18}}}



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some steps....

{{{12(100-v)+20v=18*100}}}

{{{6(100-v)+10v=9*100}}}

{{{3(100-v)+5v=9*50}}}

{{{300-3v+5v=9*50}}}

keep going until solved.....