document.write( "Question 1006041: Mr. Taylor withdrew $220 from the bank. The bank teller gave Mr. Taylor 16 bills, which were all $10 bills and $20 bills. How many $10 bills and how many $20 bills did the bank teller give Mr. Taylor?
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Algebra.Com's Answer #622174 by AnlytcPhil(1806) $\"\"$ $\"About$

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document.write( "Let the number of $10 bills be x\r\n" );
document.write( "Let the number of $20 bills be y\r\n" );
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document.write( "                      Value      Value\r\n" );
document.write( "Type       Number       of         of\r\n" );
document.write( " of          of        EACH       ALL\r\n" );
document.write( "bill        bills      bill      bills\r\n" );
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document.write( "$10 bills     x        $10      $10x\r\n" );
document.write( "$20 bills     y        $20      $20y\r\n" );
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document.write( "TOTALS       16      -----      $220\r\n" );
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document.write( " The first equation comes from the second column.\r\n" );
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document.write( "  \r\n" );
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document.write( "                 x + y = 16\r\n" );
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document.write( " The second equation comes from the last column.\r\n" );
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document.write( "             10x + 20y = 220\r\n" );
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document.write( " So we have the system of equations:\r\n" );
document.write( "           .\r\n" );
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document.write( "We solve by substitution.  Solve the first equation for y:\r\n" );
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document.write( "                x + y = 16\r\n" );
document.write( "                    y = 16 - x\r\n" );
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document.write( "Substitute (16 - x) for y in 10x + 20y = 220\r\n" );
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document.write( "     10x + 20(16 - x) = 220\r\n" );
document.write( "      10x + 320 - 20x = 220\r\n" );
document.write( "           -10x + 320 = 220\r\n" );
document.write( "                -10x = -100\r\n" );
document.write( "                   x = 10 = the number of $10 bills.\r\n" );
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document.write( "Substitute in y = 16 - x\r\n" );
document.write( "              y = 16 - (10)\r\n" );
document.write( "              y = 6 $20 bills.\r\n" );
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document.write( "Checking:  10 $10 bills is $100 and 6 $20 bills is $120\r\n" );
document.write( "            That's 16 bills.\r\n" );
document.write( "            And indeed $100 + $120 = $220\r\n" );
document.write( "Edwin

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