document.write( "Question 1121008: when the father was the same age as his daughter is now, she was 4 years old. when the daughter becomes the same age as her father is now, her father will be 79 years old. what are their ages \n" ); document.write( "

Algebra.Com's Answer #736740 by Edwin McCravy(20056) $\"\"$ $\"About$

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Let F = the Father's age\r\n" );
document.write( "Let D = the Daughter's age\r\n" );
document.write( "Let x = number of years the father is older than his daughter.\r\n" );
document.write( "Thus F-x = D.\r\n" );
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document.write( "

\n" ); document.write( "when the father was the same age as his daughter is now, she was 4 years old.
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document.write( "The father was the daughter's present age x years ago.\r\n" );
document.write( "x years ago the daughter was D-x or 4, so D-x = 4\r\n" );
document.write( "

\n" ); document.write( "when the daughter becomes the same age as her father is now, her father will
\n" ); document.write( "be 79
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document.write( "She will become the father's age x years from now.\r\n" );
document.write( "x years from now the father will be his present age plus x years, so F+x = 79.\r\n" );
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document.write( "We have three equations and three unknowns:\r\n" );
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document.write( "(1)      F-x = D\r\n" );
document.write( "(2)      D-x = 4\r\n" );
document.write( "(3)      F+x = 79\r\n" );
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document.write( "Use (1) to substitute F-x for D in (2)\r\n" );
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document.write( "     (F-x)-x = 4\r\n" );
document.write( "       F-x-x = 4\r\n" );
document.write( "(4)     F-2x = 4\r\n" );
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document.write( "Subtract equation (4) from equation (3)\r\n" );
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document.write( "(F+x)-(F-2x) = 79-4\r\n" );
document.write( "    F+x-F+2x = 75\r\n" );
document.write( "          3x = 75\r\n" );
document.write( "           x = 25\r\n" );
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document.write( "Substitute 25 for x in (2)\r\n" );
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document.write( "(2)      D-x = 4\r\n" );
document.write( "        D-25 = 4\r\n" );
document.write( "           D = 29\r\n" );
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document.write( "Substitute 25 for x in (3)\r\n" );
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document.write( "(3)      F+x = 79\r\n" );
document.write( "        F+25 = 79\r\n" );
document.write( "           F = 54\r\n" );
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document.write( "So the Father is 54 and the daughter is 29.\r\n" );
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document.write( "Edwin

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