Question 939886
Start a stop watch when they both start running
Let {{{ t }}} = the time in seconds on the stopwatch 
when the faster runner catches the slower runner
Let {{{ d }}} = the distance the faster runner 
travels until they meet
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Slower runner's equation:
(1) {{{ d - 93 = 6t }}}
Faster runner's equation:
(2) {{{ d = 12t }}}
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Substitute (2) into (1)
(1) {{{ 12t - 93 = 6t }}}
(1) {{{ 6t = 93 }}}
(1) {{{ t = 15.5 }}}
The faster runner catches the slower runner in 15.5 sec
check:
(1) {{{ d - 93 = 6*15.5 }}}
(1) {{{ d = 93 + 93 }}}
(1) {{{ d = 186 }}} m
and
(2) {{{ d = 12*15.5 }}}
(2) {{{ d = 186 }}} m
OK