Question 580831
Let {{{ x }}} = gallons of water to be added
{{{ .8*8 = 6.4 }}} gallons of boric acid in 80% solution
{{{ 6.4 / ( x + 8 ) = .5 }}}
{{{ 6.4 = .5*( x + 8 ) }}}
{{{ 6.4 = .5x + 4 }}}
{{{ .5x = 6.4 - 4 }}}
{{{ .5x = 2.4 }}}
{{{ x = 4.8 }}} 
4.8 gallons of water must be added