document.write( "Question 886171: Ann purchased 19 stamps, a mixture of 49 cents and 20 cents stamps. Find the numbers of each type of stamp if she spent $7.28. \n" ); document.write( "

Algebra.Com's Answer #535736 by jgr45(31) $\"\"$ $\"About$

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Let x = the number of 49¢ stamps, and y = the number of 20¢ stamps; and I will express the money in cents (i.e. total of 728¢ was spent).\r
\n" ); document.write( "\n" ); document.write( "So we have a two equation system:
\n" ); document.write( "49x + 20y = 728, and
\n" ); document.write( "x + y = 19.\r
\n" ); document.write( "\n" ); document.write( "We need to isolate a variable (I'll pick y)
\n" ); document.write( "y = 19 - x\r
\n" ); document.write( "\n" ); document.write( "Now substitute 19-x for y in the first equation:
\n" ); document.write( "49x + 20(19-x) = 728
\n" ); document.write( "49x + 380 - 20x = 728
\n" ); document.write( "29x + 380 = 728
\n" ); document.write( "29x = 348
\n" ); document.write( "x = 12\r
\n" ); document.write( "\n" ); document.write( "Which means y = 19-12, or 7.\r
\n" ); document.write( "\n" ); document.write( "Plug these values into first equation:
\n" ); document.write( "49(12) + 20(7) =? 728
\n" ); document.write( "588 + 140 = 728
\n" ); document.write( "728 = 728 {{check}}\r
\n" ); document.write( "\n" ); document.write( "So Ann bought 12 49¢ and 7 20¢ stamps with her $7.28 . \n" ); document.write( "

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