document.write( "Question 1143760: A family has two cars. The first car has a fuel efficiency of
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\n" ); document.write( "\n" ); document.write( "miles per gallon of gas. During one particular week, the two cars went a combined total of
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Algebra.Com's Answer #764658 by ikleyn(52910) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "Let x = fuel amount (in gallons) consumed by the first car at 35 mi/gallon, and \r\n" );
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document.write( "let y = fuel amount (in gallons) consumed by the second car at 15 mi/gallon.\r\n" );
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document.write( "From the condition, you have these two equation\r\n" );
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document.write( "      x +   y =  35  gallons    (1)\r\n" );
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document.write( "    35x + 15y = 825  miles      (2)\r\n" );
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document.write( "Simplify by dividing equation (2) by 5 (both sides). You will get\r\n" );
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document.write( "      x +   y =  35             (3)\r\n" );
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document.write( "     7x +  3y = 165             (4)\r\n" );
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document.write( "From equation (3), express  y = 35-x  and substitute it into equation (4).  You will get\r\n" );
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document.write( "     7x + 3*(35-x) = 165\r\n" );
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document.write( "     7x + 105 - 3x = 165\r\n" );
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document.write( "     7x - 3x       = 165 - 105\r\n" );
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document.write( "     4x            = 60\r\n" );
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document.write( "      x            = 60/4 = 15.\r\n" );
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document.write( "ANSWER.  First car consumed 15 gallons of gas; second car consumed the rest  35-15 = 20 gallons of gas.\r\n" );
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