Question 306077
Let {{{x}}} = gallons of pure acid to add
{{{(x + .6*4)/(x + 4) = .8}}}
{{{x + 2.4 = .8*(x + 4)}}}
{{{x + 2.4 = .8x + 3.2}}}
{{{.2x = .8}}}
{{{x = 4}}}
4 gallons of pure acid must be added
check:
{{{(4 + .6*4)/(4 + 4) = .8}}}
{{{6.4/8 = .8}}}
{{{.8 = .8}}}
OK