document.write( "Question 578644: On Tuesday, Wendy picked up three doughnuts and four large coffees for the backroom staff; she paid $4.91. On Thursday Bruce picked up five doughnuts and six large coffees for the same group; he paid $7.59. What the cost of one doughnut, and of one large coffee? \n" ); document.write( "

Algebra.Com's Answer #370715 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = cost of 1 donut
\n" ); document.write( "Let $\"+b+\"$ = cost of 1 lg coffee
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"+3a+%2B+4b+=+491+\"$ ( in cents )
\n" ); document.write( "(2) $\"+5a+%2B+6b+=+759+\"$ ( in cents )
\n" ); document.write( "Multiply both sides of (1) by $\"+5+\"$
\n" ); document.write( "Multiply both sides of (2) by $\"+3+\"$
\n" ); document.write( "and subtract (2) from (1)
\n" ); document.write( "(1) $\"+15a+%2B+20b+=+2455+\"$
\n" ); document.write( "(2) $\"+-15a+-+18b+=+-+2277+\"$
\n" ); document.write( " $\"+2b+=+178+\"$
\n" ); document.write( " $\"+b+=+89+\"$
\n" ); document.write( "Plug this back into (1)
\n" ); document.write( "(1) $\"+3a+%2B+4%2A89+=+491+\"$
\n" ); document.write( "(1) $\"+3a+=+491+-+356+\"$
\n" ); document.write( "(1) $\"+3a+=+135+\"$
\n" ); document.write( "(1) $\"+a+=+45+\"$
\n" ); document.write( "One donut costs 45 cents
\n" ); document.write( "One lg coffee cost 89 cents
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+5%2A45+%2B+6%2A89+=+759+\"$
\n" ); document.write( "(2) $\"+225+%2B+534+=+759+\"$
\n" ); document.write( "(2) $\"+759+=+759+\"$
\n" ); document.write( "OK \n" ); document.write( "

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