Question 363069
Let A be the amount of 20% solution, B the amount of 50% solution.
1.{{{A+B=600}}}
.
.
{{{20A+50B=30(600)}}}
2.{{{2A+5B=1800}}}
Multiply eq. 1 by (-2) and add to eq. 2,
{{{-2A-2B+2A+5B=-1200+1800}}}
{{{3B=600}}}
{{{highlight(B=200)}}}liters
Then from eq. 1,
{{{A+200=600}}}
{{{highlight(A=400)}}}liters