Question 428537
Starts as  {{{0.8(140)}}} liters of pure alcohol.


Add x liters of distilled water to make 70% alcohol.
{{{(0.8*140)/(x+140)=0.7}}}


Simple algebra.

{{{0.8*140=0.7x+0.7*140}}}

{{{0.8*140-0.7*140=0.7x}}}

{{{0.1*140=0.7x}}}

{{{x=(0.1*140)/0.7}}}

{{{x=140/7}}}

{{{highlight(x=20)}}}