Question 578751
Let {{{x}}} = quarts of pure antifreeze to be added
given:
{{{ .3*2 = .6 }}} quarts of pure antifreeze in 30% solution
{{{ ( x + .6 ) / ( x + 2 ) = .5 }}}
{{{ x + .6 = .5*( x + 2 ) }}}
{{{ x + .6 = .5x + 1 }}}
{{{ .5x = .4 }}}
{{{ x = .8 }}}
.8 quarts of pure antifreeze must be added
check:
{{{ ( .8 + .6 ) / ( .8 + 2 ) = .5 }}} 
{{{ 1.4 / 2.8 = .5 }}}
{{{ 1.4 = .5*2.8 }}}
{{{ 1.4 = 1.4 }}}
OK