document.write( "Question 905379: During his semester break, Zack went on a road trip from Berlin to Prague. He travelled part of the journey at a speed of 90 km/h and the rest at 80 km/h. Given that Zack travelled a total distcance of 690 km in 8 hours, form a pair of simultaneous equations to find the distance that he covered at 80 km/h.
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Algebra.Com's Answer #549258 by ankor@dixie-net.com(22740)\"\" \"About 
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He travelled part of the journey at a speed of 90 km/h and the rest at 80 km/h.
\n" ); document.write( " Given that Zack travelled a total distance of 690 km in 8 hours, form a pair of simultaneous equations to find the distance that he covered at 80 km/h.
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\n" ); document.write( "let x = time at 80 km/hr
\n" ); document.write( "let y = time at 90
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\n" ); document.write( "x + y = 8
\n" ); document.write( "and
\n" ); document.write( "80x + 90y = 690
\n" ); document.write( "Simplify, divide eq by 10
\n" ); document.write( "8x + 9y = 69
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\n" ); document.write( "Multiply the 1st equation by 9, subtract the above equation
\n" ); document.write( "9x + 9y = 72
\n" ); document.write( "8x + 9y = 69
\n" ); document.write( "--------------Subtractions eliminates y, find x
\n" ); document.write( "x = 3 hrs at 80 km/hr
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\n" ); document.write( "I'll let you confirm this, find y and check these values for x and y in both original equations \n" ); document.write( "
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