Question 1130639
x of 25%
y of 35%
z of 65%
-
{{{z/y=2}}}
{{{z=2y}}}



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He wants to use all three solutions to obtain a mixture of 102 liters containing 40% acid, 
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{{{x+y+2y=102}}}
{{{x+3y=102}}}


Accounting for the desired percentages and amount of pure acid
{{{25x+35y+65(2y)=40*102}}}

Simplify this pure-acid equation.

{{{25x+(35+2*65)y=40*102}}}

{{{25x+165y=40*102}}}
divide both sides by 5,
{{{5x+33y=8*102}}}
{{{5x+33y=816}}}


Simpler system in variables x and y:
{{{system(x+3y=102,5x+33y=816)}}}


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You should get, if continue with Elimination Method,
{{{highlight_green(y=17)}}}
From that you should find that {{{highlight_green(z=34)}}}.......
and {{{highlight_green(x=51)}}}.