Question 708332
EDIT: Added explanation after the end.


Water with "nothing else" in it will have 0% acid.  You have 25% acid and you want to add water, of 0% acid to make 5% acid.


How much acid will be?
How much volume of mixture will result?
What concentration of acid must result?
----------> Rational Equation:


Let x be how much water
Let y be how much 25% acid


{{{(0*x+25*y)/200=5}}}
AND
{{{x+y=200}}}


Solve for y in the rational equation.  Use that result in the volume sum equation to find x.


FURTHER EXPLANATION:  The reason I said that last part is because {{{0*x=0}}} in the rational equation.  This means the rational equation only has one variable, the y.  One single linear y, easy to solve.  Then use the volume sum equation to find x.