Question 628752
Let {{{ b }}} = speed of boat in still water
Let {{{ c }}} = speed of water current
given:
(1) {{{ b - c = 9 }}}
(2) {{{ b + c = 15 }}}
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Add the equations
{{{ 2b = 24 }}}
{{{ b = 12 }}}
and
(2) {{{ 12 + c = 15 }}}
(2) {{{ c = 15 - 12 }}}
(2) {{{ c = 3 }}}
The speed of the boat in still water is 12 mi/hr
The speed of the water current is 3 mi/hr