Question 921838
Let {{{ x }}} = oz of pure chocolate to be added
{{{ .5*230 = 115 }}} oz of pure chocolate in 50% chocolate
{{{ (( x + 115 )) / (( x + 230 )) = .75 }}}
{{{ x + 115 = .75*( x + 230 ) }}}
{{{ x + 115 = .75x + 172.5 }}}
{{{ .25x = 57.5 }}}
{{{ x = 230 }}}
230 oz must be added
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check:
{{{ (( x + 115 )) / (( x + 230 )) = .75 }}}
{{{ (( 230 + 115 )) / (( 230 + 230 )) = .75 }}}
{{{ 345 / 460 = .75 }}}
{{{ 345 = .75*460 }}}
{{{ 345 = 345 }}} 
OK