document.write( "Question 133416: Alice is 4 years younger than Betty and Carl is 3 times as old as Alice. Five years ago, Carl's age was 3 years less than twice the sum of the girls' ages then. How old is Carl now? \n" ); document.write( "
Algebra.Com's Answer #97590 by solver91311(24713)\"\" \"About 
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Alice is 4 years younger than Betty and Carl is 3 times as old as Alice. Five years ago, Carl's age was 3 years less than twice the sum of the girls' ages then. How old is Carl now?\r
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\n" ); document.write( "\n" ); document.write( "Alice now: a
\n" ); document.write( "Betty now: b
\n" ); document.write( "Carl now: c\r
\n" ); document.write( "\n" ); document.write( "\"a=b-4\" Alice is 4 years younger than Betty
\n" ); document.write( "\"c=3a\"\r
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\n" ); document.write( "\n" ); document.write( "Carl five years ago: c - 5
\n" ); document.write( "Alice five years ago: a - 5
\n" ); document.write( "Betty five years ago: b - 5\r
\n" ); document.write( "\n" ); document.write( "The sum of the girls' ages five years ago: \"%28a-5%29%2B%28b-5%29\"
\n" ); document.write( "Twice the sum... \"2%28%28a-5%29%2B%28b-5%29%29=2a%2B2b-20\"
\n" ); document.write( "Carl five years ago was 3 years less than the above expression, so:\r
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\n" ); document.write( "\n" ); document.write( "\"c-5=2a%2B2b-20-3\"
\n" ); document.write( "\"c=2a%2B2b-18\"\r
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\n" ); document.write( "\n" ); document.write( "Since \"a=b-4\", \"b+=+a%2B4\"\r
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\n" ); document.write( "\n" ); document.write( "Now substitute:
\n" ); document.write( "\"3a=2a%2B2%28a%2B4%29-18\"\r
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\n" ); document.write( "\n" ); document.write( "\"3a=2a%2B2a%2B8-10\"\r
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\n" ); document.write( "\n" ); document.write( "\"3a=4a-10\"
\n" ); document.write( "\"-a=-10\"
\n" ); document.write( "\"a=10\"\r
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\n" ); document.write( "\n" ); document.write( "So Alice is 10 now, which means that Betty is 10 + 4 = 13, and Carl is 3 * 10 = 30.\r
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\n" ); document.write( "\n" ); document.write( "Check the answer:
\n" ); document.write( "5 years ago, Carl would have been 25, Alice, 5, and Betty, 9. the sum of their ages then would have been 14, twice 14 is 28, 3 years less than that is 25. Answer checks.
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