Question 959278
The 1st car has a head start of:
{{{ d[1] = 75*(12/60) }}}
{{{ d[1] = 75/5 }}}
{{{ d[1] = 15 }}} km
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Let {{{ d }}} = the distance in km the 2nd car 
travels until it catches the 1st car
Let {{{ t }}} = the time in hrs it takes the
2nd car to catch the 1st car
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Start a stop watch when the 2nd car leaves
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Equation for 1st car:
(1) {{{ d - 15 = 75t }}}
Equation for 2nd car:
(2) {{{ d = 195t }}}
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By substitution:
(1) {{{ 195t - 15 = 75t }}}
(1) {{{ 120t = 15 }}}
(1) {{{ t = 1/8 }}}
{{{ (1/8)*60 = 7.5 }}}
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The 2nd car catches the 1st car in 7.5 min
The time would be 3 PM + 12 min + 7.5 min
or 3:19:30 PM
check:
(1) {{{ d - 15 = 75t }}}
(1) {{{ d - 15 = 75*(1/8) }}}
(1) {{{ d = 9.375 + 15 }}}
(1) {{{ d = 24.375 }}}
and
(2) {{{ d = 195t }}}
(2) {{{ d = 195*(1/8) }}}
(2) {{{ d = 24.375 }}}
OK