Question 917386
We have 15 liter of 30% solution
We want to add some 5% solution  to make   10% solution
0.05*x+0.3*15=0.1(15+x)
0.05*x+4.5=1.5+0.1x
0.05x-0.1x=1.5-4.5
-0.05x=-3
x=60 liter at 5% (3) is added to 15 liter at 30%(4.5) to make 10% of 75 liter(7.5)
check
0.05*60+0.3*15=0.1(15+60)
3+4.5=0.1(75)
7.5=7.5
ok
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