Question 543533
Let {{{ x }}} = pounds of Spanish peanuts needed
In words:
( total cost of mixture ) / ( total pounds of mixture ) = $3.40
given:
{{{ 10 + x }}} =  total pounds of mixture
{{{ 10*3.5 = 35 }}} = cost of Virginia peanuts used
{{{ 3x }}} = cost of Spanish peanuts used
--------------
{{{ ( 35 + 3x ) / ( 10 + x ) = 3.4 }}}
{{{ 35 + 3x = 3.4*( 10 + x ) }}}
{{{ 35 + 3x = 34 + 3.4x }}}
{{{ .4x = 1 }}}
{{{ x = 2.5 }}}
She needs 2.5 pounds of Spanish peanuts
check answer:
{{{ ( 35 + 3x ) / ( 10 + x ) = 3.4 }}}
{{{ ( 35 + 3*2.5 ) / ( 10 + 2.5 ) = 3.4 }}}
{{{ 42.5 / 12.5 = 3.4 }}}
{{{ 42.5 = 42.5 }}}
OK