Question 788146
Let {{{ c }}} = speed of the river ( the current ) in km/hr
Let {{{ s }}} = the speed of the boat in still water in km/hr
{{{ s + c }}} = speed of boat going downstream
{{{ s - c }}} = speed of boat going upstream
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It sounds like there is a round trip of {{{ 2*36 }}} km
which means the (+) and (-) effects of the current
cancel out 
Making round trip:
(1) {{{ 2*36 = s*8 }}}
(1) {{{ 72 = 8s }}}
(1) {{{ s = 9 }}}
Going upstream:
(2) {{{ 60 = ( s - c )*10 }}}
(2) {{{ 60 = ( 9 - c )*10 }}}
(2) {{{ 60 = 90- - 10c }}}
(2) {{{ 10c = 90 - 60 }}}
(2) {{{ 10c = 30 }}}
(2) {{{ c = 3 }}}
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The speed of the boat in still water is 9 km/hr
The speed of the river is 3 km/hr