Answer
21.1 mph
Work Step by Step
340 miles one way
14 hours downriver
19 hours upriver
$340 = (x+y)*14$
$340 = (x-y)*19$
$340 = (x+y)*14$
$14x+14y=340$
$340 = (x-y)*19$
$19x-19y=340$
$14x+14y=19x-19y$
$14y=5x-19y$
$33y=5x$
$33y/5=5x/5$
$33y/5=x$
$14x+14y=340$
$14*(33y/5)+14y=340$
$462y/5+14y=340$
$462y+70y/5=340$
$532y/5=340$
$532y/5*5=340*5$
$532y=1700$
$532y/532=1700/532$
$y=3.2$
$14x+14y=340$
$14x+14*3.2=340$
$14x+44.8=340$
$14x=295.2$
$14x/14 =295.2/14$
$x=21.1$