Question 996841
With that description, he must have concentrations as all w/v  OR  v/v exclusively.


y, how much of the pure acid to add.


{{{(20*40+100*y)/(y+20)=60}}}


{{{(2*40+10y)/(y+20)=6}}}


{{{(40+5y)/(y+20)=3}}}


{{{40+5y=3y+60}}}

{{{2y=20}}}


{{{highlight(y=10)}}}