Question 589084
Let {{{x}}} = pounds of $30/pound coffee needed
{{{ 30*80 = 2400 }}} = cost in dollars of $80/pound coffee
{{{ ( 30x + 2400 ) / ( x + 30 ) = 60 }}}
{{{ 30x + 2400 = 60*( x + 30 ) }}}
{{{ 30x + 2400 = 60x  + 1800 }}}
{{{ 30x = 2400 - 1800 }}}
{{{ 30x = 600 }}}
{{{ x = 20 }}}
20 pounds of $30/pound coffee is needed
check:
{{{ ( 30x + 2400 ) / ( x + 30 ) = 60 }}}
{{{ ( 30*20 + 2400 ) / ( 20 + 30 ) = 60 }}}
{{{ ( 600 + 2400 ) / 50 = 60 }}}
{{{ 3000 = 60*50 }}}
{{{ 3000 = 3000 }}}
OK