Question 876290
 <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi
average speed = {{{36/8}}} = 4.5mph
r = 2c where c is the rate of the current
{{{ 18/(3c) + 18/c = 8hr}}}| |Multiplying thru by 3c so as all denominators = 1
    18 + 54 = 24c
         72/24 = c = 3mph