Question 879991
Let {{{ d }}} = the distance he travels
Let {{{ t }}} = the " on time " time
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(1) {{{ d = 24*( t + 5/60 ) }}}
(2) {{{ d = 30*( t - 4/60 ) }}}
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By substitution:
{{{ 24*( t + 1/12 ) = 30*( t - 1/15 ) }}}
{{{ 24t + 24/12 = 30t - 30/15 }}}
{{{ 6t = 2 + 2 }}}
{{{ t = 2/3 }}}
and
(1) {{{ d = 24*( t + 5/60 ) }}}
(1) {{{ d = 24*( 2/3 + 5/60 ) }}}
(1) {{{ d = 24*( 40/60 + 5/60 ) }}}
(1) {{{ d = 24*( 45/60 ) }}}
(1) {{{ d = 24*( 3/4 ) }}}
(1) {{{ d = 18 }}} 
The destination is 18 km away
check:
(1) {{{ d = 24*( t + 5/60 ) }}}
(1) {{{ 18 = 24*( 40/60 + 5/60 ) }}}
(1) {{{ 18/24 = 45/60 }}}
(1) {{{ 3/4 = 3/4 }}}
OK
You can check (2)