Question 98712
Let x= amount drained and replaced by a 70% solution

Amount of pure chemical remaining after x amount was drained out is 0.30(80-x)

Amount of pure chemical added back in is 0.70x

Amount of pure chemical in the final mixture is 0.40*80

Amount of pure chemical in our solution before they are mixed together=amount of pure chemical after they are mixed so our equation to solve is:

0.30(80-x)+0.70x=0.40*80  get rid of parens
24-0.30x+0.70x=32  subtract 24 from both sides

24-24-0.30x+0.70x=32-24  collect like terms

0.40x=8 divide both sides by 0.40

x=20 liters------------amount drained and replaced by a 70% solution

CK

60*0.30+0.70*20=0.40*80
18+14=32
32=32



Hope this helps---ptaylor