Question 884311
Let {{{ x }}} = liters of water to be added
{{{ 12*.333 = 4 }}} liters of acid
 in 33 1/3 % solution 
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{{{ 4 / ( x + 12 ) = .2 }}}
{{{ 4 = .2*( x + 12 ) }}}
{{{ 4 = .2x + 2.4 }}}
{{{ .2x = 1.6 }}}
{{{ x = 8 }}}
8 liters of water need to be added