document.write( "Question 731272: Andrew, Beth, and Carlos are painting a house. If Andrew and Beth paint the house together, it will take 10 days. If Beth and Carlos paint the house together , it will take 6 days. If Andrew, Beth and Carlos all paint together, it will take 5 days. How long will it take Carlos to paint the house alone? \n" ); document.write( "
Algebra.Com's Answer #447072 by josmiceli(19441)\"\" \"About 
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Add rates of painting to get rate of
\n" ); document.write( "painting together
\n" ); document.write( "Let \"+a+\" = Andrew's time in days to paint house alone
\n" ); document.write( "Let \"+b+\" = Beth's time in days to paint house alone
\n" ); document.write( "Let \"+c+\" = Carlos's time in days to paint house alone
\n" ); document.write( "For example:
\n" ); document.write( "( 1 house ) / ( a days ) + ( 1 house ) / ( b days ) = ( 1 house ) / ( 10 days )
\n" ); document.write( "(1) \"+1%2Fa+%2B+1%2Fb+=+1%2F10+\"
\n" ); document.write( "(2) \"+1%2Fb+%2B+1%2Fc+=+1%2F6+\"
\n" ); document.write( "(3) \"+1%2Fa+%2B+1%2Fb+%2B+1%2Fc+=+1%2F5+\"
\n" ); document.write( "---------------------------
\n" ); document.write( "make these substitutions:
\n" ); document.write( "\"+1%2Fa+=+R%5Ba%5D+\"
\n" ); document.write( "\"+1%2Fb+=+R%5Bb%5D+\"
\n" ); document.write( "\"+1%2Fc+=+R%5Bc%5D+\"
\n" ); document.write( "-------------
\n" ); document.write( "(1) \"+R%5Ba%5D+%2B+R%5Bb%5D+=+1%2F10+\"
\n" ); document.write( "(2) \"+R%5Bb%5D+%2B+R%5Bc%5D+=+1%2F6+\"
\n" ); document.write( "(3) \"+R%5Ba%5D+%2B+R%5Bb%5D+%2B+R%5Bc%5D+=+1%2F5+\"
\n" ); document.write( "----------------------------
\n" ); document.write( "(1) \"+R%5Ba%5D+=+1%2F10+-+R%5Bb%5D+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+R%5Bc%5D+=+1%2F6+-+R%5Bb%5D+\"
\n" ); document.write( "------------------------
\n" ); document.write( "By substitution:
\n" ); document.write( "(3) \"+1%2F10+-+R%5Bb%5D+%2B+R%5Bb%5D+%2B+1%2F6+-+R%5Bb%5D+=+1%2F5+\"
\n" ); document.write( "(3) \"+R%5Bb%5D+=+1%2F10+%2B+1%2F6+-+1%2F5+\"
\n" ); document.write( "(3) \"+R%5Bb%5D+=+3%2F30+%2B+5%2F30+-+6%2F30+\"
\n" ); document.write( "(3) \"+R%5Bb%5D+=+2%2F30+\"
\n" ); document.write( "(3) \"+R%5Bb%5D+=+1%2F15+\"
\n" ); document.write( "and
\n" ); document.write( "(2) \"+R%5Bc%5D+=+1%2F6+-+R%5Bb%5D+\"
\n" ); document.write( "(2) \"+R%5Bc%5D+=+1%2F6+-+1%2F15+\"
\n" ); document.write( "(2) \"+R%5Bc%5D+=+15%2F90+-+6%2F90+\"
\n" ); document.write( "(2) \"+R%5Bc%5D+=+9%2F90+\"
\n" ); document.write( "(2) \"+R%5Bc%5D+=+1%2F10+\"
\n" ); document.write( "It will take Carlos 10 days to paint the house alone
\n" ); document.write( "check:
\n" ); document.write( "(1) \"+R%5Ba%5D+=+1%2F10+-+R%5Bb%5D+\"
\n" ); document.write( "(1) \"+R%5Ba%5D+=+1%2F10+-+1%2F15+\"
\n" ); document.write( "(1) \"+R%5Ba%5D+=+3%2F30+-+2%2F30+\"
\n" ); document.write( "(1) \"+R%5Ba%5D+=+1%2F30+\"
\n" ); document.write( "------------------
\n" ); document.write( "(3) \"+R%5Ba%5D+%2B+R%5Bb%5D+%2B+R%5Bc%5D+=+1%2F5+\"
\n" ); document.write( "(3) \"+1%2F30+%2B+1%2F15+%2B+1%2F10+=+1%2F5+\"
\n" ); document.write( "(3) \"+1%2F30+%2B+2%2F30+%2B+3%2F30+=+1%2F5+\"
\n" ); document.write( "(3) \"+6%2F30+=+1%2F5+\"
\n" ); document.write( "(3) \"+1%2F5+=+1%2F5+\"
\n" ); document.write( "OK\r
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