document.write( "Question 339157: It takes my brother 15 min to clean one window. It takes me 20 minutes to clean one window. How long will it take us to clean 12 windows. \n" ); document.write( "
Algebra.Com's Answer #243088 by nerdybill(7384)\"\" \"About 
You can put this solution on YOUR website!
It takes my brother 15 min to clean one window. It takes me 20 minutes to clean one window. How long will it take us to clean 12 windows.
\n" ); document.write( ".
\n" ); document.write( "Let x = minutes to clean 12 windows together
\n" ); document.write( "the
\n" ); document.write( "x(1/15 + 1/20) = 12
\n" ); document.write( "multiplying both sides by 300:
\n" ); document.write( "x(20 + 15) = 3600
\n" ); document.write( "35x = 3600
\n" ); document.write( "x = 3600/35
\n" ); document.write( "x = 102.86 minutes\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "
\n" );