Question 771162
Add v mL of 60% acid to u mL of 30% acid solution to produce 810 mL of 50% acid solution.


{amount of just acid}/{amount of resulting solution}={concentration of resulting solution}


{{{(30u+60v)/810=50}}} AND YOU WILL ALSO NEED {{{highlight(u+v=810)}}}


Simplify the rational equation quickly:
{{{(3u+6v)/810=5}}}
{{{(u+2v)/270=5}}}
then managing symbols,
{{{u+2v=270*5}}}
{{{highlight(u+2v=1350)}}}, easier to work with this form.


The rest left unfinished so you can do the rest.  Two equations for the system, highlighted.