a red light winks every 6 seconds, a white one every 10 seconds, and a green one every 14 seconds. how often they wink together?

Answer 1

6 = 2*3
10 = 2*5
14 = 2*7

LCM(6,10,14) = 2*3*5*7 = 210

so, every 210 seconds they will blink at the same time