Question

solve no 4 in full process

Answer 1

the traffic lights lightened after24,36,42 seconds
they are lightened at 6:00 am
they will glow at same time after (LCM of 24,36,42)seconds
lcm of 24,36,42 is 504
thus they will occur after 504 seconds or 8 minutes 24 seconds
thus they will glow at 6:8:24am

Answer 2

Just google it why do you ask subjective questions here