<PRE><B>Question 509589</B>
St. Lawerence River = x
Zambezi River = 2x 
Rhine River = x-160 
Amazon = 800+5(x-160)
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Amazon = (St. Lawerence River + Zambezi River + Rhine River)+1440
800+5(x-160) = x+(2x)+(x-160)+1440
800+5x-800= x+2x+x-160+1440
5x=4x+1280
5x= 4x+1280
5x-4x=1280
x=1280
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Amazon = 800+5(x-160)
Put the value of x in above equation
Amazon = 800+5(1280-160)
Amazon=800+5(1120)
Amazon = 800+5600
Amazon=6400 km
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