Question 410742
Let {{{x}}} = pounds of Kona beans needed
In words:
(cost of French Roast in mixture + cost of Kona in mixture) /(total pounds of mixture) = 
(cost per pound of mixture)
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given:
Cost of French roast in mixture = {{{7.5*12 = 90}}} dollars
Cost of Kona in mixture  = {{{11.5x}}}
Toyal pounds of mixture = {{{12 + x}}}
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{{{(90 + 11.5x)/(12 + x) = 10/1}}}
{{{90 + 11.5x = 10*(12 + x)}}}
{{{90 + 11.5x = 120 + 10x}}}
{{{1.5x = 30}}}
{{{x = 20}}}
20 pounds of Kona coffee beans are needed
check answer:
{{{(90 + 11.5x)/(12 + x) = 10/1}}}
{{{(90 + 11.5*20)/(12 + 20) = 10/1}}}
{{{(90 + 230) / 32 = 10}}}
{{{320 = 320}}}
OK