document.write( "Question 186415: a merchant has coffee worth $20 a pound that she wishes to mix with 80 pounds of coffee worth $90 a pound to get a mixture that can be sold for $60 a pound. how many pounds of the $20 coffee should be used? \n" ); document.write( "

Algebra.Com's Answer #139706 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"a\"$ = pounds of $20 coffee used
\n" ); document.write( "given:
\n" ); document.write( " $\"20a\"$ = cost in dollars of $20 coffee used
\n" ); document.write( " $\"80%2A90+=+7200\"$ = cost in dollars of $90 coffee used
\n" ); document.write( " $\"a+%2B+80\"$ = pounds of coffee in final mixture
\n" ); document.write( " $\"60%2A%28a+%2B+80%29\"$ = cost in dollars of final mixture
\n" ); document.write( "-------------------
\n" ); document.write( " $\"20a+%2B+7200+=+60%2A%28a+%2B+80%29\"$
\n" ); document.write( " $\"20a+%2B+7200+=+60a+%2B+4800\"$
\n" ); document.write( " $\"40a+=+2400\"$
\n" ); document.write( " $\"a+=+60\"$
\n" ); document.write( "60 pounds of $20 coffee must be used
\n" ); document.write( "check:
\n" ); document.write( " $\"20a+%2B+7200+=+60%2A%28a+%2B+80%29\"$
\n" ); document.write( " $\"20%2A60+%2B+7200+=+60%2A%2860+%2B+80%29\"$
\n" ); document.write( " $\"1200+%2B+7200+=+60%2A140\"$
\n" ); document.write( " $\"8400+=+8400\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );