document.write( "Question 858150: A boat can go 72 miles downstream in 3 hours, and can make the return trip in 4 hours. Find the speed of the boat in still water. \n" ); document.write( "
Algebra.Com's Answer #517293 by tommyt3rd(5050)\"\" \"About 
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up: (s+c)3=72,
\n" ); document.write( "down: (s-c)4=72\r
\n" ); document.write( "\n" ); document.write( "adding...\r
\n" ); document.write( "\n" ); document.write( "2s=72(1/3+1/4)\r
\n" ); document.write( "\n" ); document.write( "then...\r
\n" ); document.write( "\n" ); document.write( "s=21\r
\n" ); document.write( "\n" ); document.write( "boat speed: 21mph
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