document.write( "Question 498948: A plane traveled 864 miles to Shanghai and back. The trip there was with the wind. It took 9 hours. The trip back was into the wind. The trip back took 18 hours. What is the speed of the plane in still air? What is the speed of the wind? \n" ); document.write( "
Algebra.Com's Answer #337372 by mananth(16946)\"\" \"About 
You can put this solution on YOUR website!
Plane speed =x mph
\n" ); document.write( "Wind speed =y mph
\n" ); document.write( "against wind x-y 18.00 hours
\n" ); document.write( "with windx+y 9.00 hours
\n" ); document.write( "
\n" ); document.write( "Distance = same= 864 miles
\n" ); document.write( "t=d/r
\n" ); document.write( "864 / ( x - y )= 18.00
\n" ); document.write( "18 ( x - y ) = 864.00
\n" ); document.write( "18 x -18 y = 864 ....................1
\n" ); document.write( "864 / ( x + y )= 9.00
\n" ); document.write( "9.00 ( x + y ) = 864
\n" ); document.write( "9.00 x + 9.00 y = 864 ...............2
\n" ); document.write( "Multiply (1) by 1.00
\n" ); document.write( "Multiply (2) by 2.00
\n" ); document.write( "we get
\n" ); document.write( "18 x + -18 y = 864
\n" ); document.write( "18 x + 18 y = 1728
\n" ); document.write( "36 x = 2592
\n" ); document.write( "/ 36
\n" ); document.write( "x = 72 mph
\n" ); document.write( "
\n" ); document.write( "plug value of x in (1)
\n" ); document.write( "18 x -18 y = 864
\n" ); document.write( "1296 -18 y = 864
\n" ); document.write( "-18 y = 864 -1296
\n" ); document.write( "-18 y = -432
\n" ); document.write( " y = 24 mph
\n" ); document.write( " \n" ); document.write( "
\n" );