document.write( "Question 931172: a box contains 30 coins (5 cents, 10 cents, 25 cents and 50 cents)with a total value of Dollar 6.45. There are twice as many 10 cents coins as 25 cents coins and 2 more 50cents coins than 5 cents coins. How many of each kind of coins are there?
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Algebra.Com's Answer #565464 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "x+y+z+w=30\r\n" );
document.write( "5x+10y+25z+50w=645\r\n" );
document.write( "y=2z\r\n" );
document.write( "w=x+2\r\n" );
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document.write( "Substitute 2z fo y and x+2 for w in the first two equations:\r\n" );
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document.write( "x+2z+z+x+2=30      5x+10(2z)+25z+50(x+2)=645\r\n" );
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document.write( "Simplify\r\n" );
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document.write( "2x+3z+2=30         5x+20z+25z+50x+100=645\r\n" );
document.write( "  2x+3z=28                55x+45z+100=645\r\n" );
document.write( "                              55x+45z=545\r\n" );
document.write( "                               11x+9z=109\r\n" );
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document.write( "So we have the system:\r\n" );
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document.write( "  2x+3z=28\r\n" );
document.write( " 11x+9z=109\r\n" );
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document.write( "Multiply the top equation by -3 and add the bottom equation:\r\n" );
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document.write( " -6x-9z=-84\r\n" );
document.write( " 11x+9z=109\r\n" );
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document.write( "  5x   = 25\r\n" );
document.write( "      x=5\r\n" );
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document.write( "You finish:\r\n" );
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document.write( "x = 5, y = 12, z = 6, w=7\r\n" );
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document.write( "Edwin
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