Question 1107731
Start a stopwatch when the 2nd
bus leaves the city at 11 AM.
Let {{{ t }}} = the time in hrs on the
stopwatch when the buses are 
460 km apart
Let {{{ d[1] }}} = distance in km the 1st bus travels
from 8 AM to 11 AM
Let {{{ d }}} = distance in km the 2nd bus travels
during time {{{ t }}} on the stopwatch
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Equation for the 1st bus from 8 AM to 11 AM
(1) {{{ d[1] = 70*3 }}}
Equation for the 2nd bus:
(2) {{{ d = 55t }}}
Equation for the 1st bus during time {{{ t }}} on stopwatch
(3) {{{ 460 - d[1] - d = 70t }}}
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(1) {{{ d[1] = 210 }}}
Plug (2) into (3)
(3) {{{ 460 - 210 - 55t = 70t }}}
(3) {{{ 250 - 55t = 70t }}}
(3) {{{ 125t = 250 }}}
(3) {{{ t = 2 }}}
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2 hrs after 11 AM, or at 1 PM, the buses are 460 km apart
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check the answer:
(2) {{{ d = 55t }}}
(2) {{{ d = 55*2 }}}
(2) {{{ d = 110 }}} km
The first bus travels {{{ 460 - 110 = 560 }}} km from 
8 AM to 1 PM, or 5 hrs
{{{ 350 = r*5 }}}
{{{ r = 70 }}} km/hr
OK