Question 921283
Let {{{ s }}} = the speed of the ferry in still water
Let {{{ d }}} = the distance between the towns
(1) {{{ s - 5 = d/2 }}} = speed going from B to A
(2) {{{ s + 5 = d/1.5 }}} = speed going from A to B
---------------------
(1) {{{ 2s - 10 = d }}}
and
(2) {{{ 1.5s + 7.5 = d }}}
----------------------
By substitution:
{{{ 1.5s + 7.5 = 2s - 10 }}}
{{{ .5s = 17.5 }}}
{{{ s = 35 }}}
and
(1) {{{ 2s - 10 = d }}}
(1) {{{ 2*35 - 10 = d }}}
(1) {{{ d = 70 - 10 }}}
(1) {{{ d = 60 }}}
The towns are 60 mi apart
----------
check:
(2) {{{ 1.5s + 7.5 = d }}}
(2) {{{ 1.5*35 + 7.5 = 60 }}}
(2) {{{ 52.5 + 7.5 = 60 }}}
(2) {{{ 60 = 60 }}}
OK