Question 542706
Let {{{ c }}} = speed of current
Let {{{ k }}} = kayaker's speed in still water
Let {{{ t }}} = time to go 20 miles upstream
{{{ k - c }}}  = speed going upstream
given:
{{{ c = 5 }}} mi/hr
{{{ k = 12 }}} mi/hr
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{{{ 20 = (k - c)*t }}}
{{{ 20 = (12 - 5)*t }}}
{{{ t = 20 / 7 }}}
{{{ t = 2.857 }}} hrs
{{{ .857*60 = 51 }}} min
It will take the kayaker 2 hrs and 51 min