Question 512591
Going to the resort island:
(1) {{{ d = 20t[1] }}}
Coming back:
(2) {{{ d = 10t[2] }}}
(3) {{{ t[1] + t[2] = 6 }}}
Substitute (1) into (2)
(2) {{{ 20t[1] = 10t[2] }}}
(2) {{{ t[2] = 2t[1] }}}
Substitute (2) into (3)
(3) {{{ t[1] + 2t[1] = 6 }}}
(3) {{{ t[1] = 2 }}}
Plug this result into (1)
(1) {{{ d = 20*2 }}}
(1) {{{ d = 40 }}}
The island is 40 mi from the harbor
check:
(2) {{{ t[2] = 2t[1] }}}
(2) {{{ t[2] = 2*2 }}}
(2) {{{ t[2] = 4 }}} hrs
and
(2) {{{ d = 10t[2] }}}
(2) {{{ d = 10*4 }}}
(2) {{{ d = 40 }}}
OK