document.write( "Question 870475: In a group of 14 children some are nine years old and the rest are eleven years old. When the ages of the 14 children are added together the total is 138 years. How many nine-year-old children are there? \n" ); document.write( "
Algebra.Com's Answer #524882 by ankor@dixie-net.com(22740)\"\" \"About 
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In a group of 14 children some are nine years old and the rest are eleven years old.
\n" ); document.write( "let a = no. of 9 yr old kids
\n" ); document.write( "let b = no. of 11 yr olds
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\n" ); document.write( "a + b = 14
\n" ); document.write( "b = (14-a)
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\n" ); document.write( " When the ages of the 14 children are added together the total is 138 years.
\n" ); document.write( "9a + 11b = 138
\n" ); document.write( "replace b with (14-a)
\n" ); document.write( "9a + 11(14-a) = 138
\n" ); document.write( "9a + 154 - 11a = 138
\n" ); document.write( "9a - 11a = 138 - 154
\n" ); document.write( "-2a = -16
\n" ); document.write( "a = -16/-2
\n" ); document.write( "a = +8 nine yr old
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\n" ); document.write( ":
\n" ); document.write( "Check this, find no. of 11 yr olds: 14-8 = 6
\n" ); document.write( "then
\n" ); document.write( "8(9) + 6(11) = 138\r
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