How to answer this question? So, I have this question, and I am wondering how to answer it. **question:** bulb nr 1 blinks `every 6 seconds.` bulb nr 2 blinks `every 7 seconds.` bulb nr 3 blinks `every 28 seconds.` Suddenly, they all blink at once. How long time until they blink at once again? I am trying to figure out a formula to solve it, any help?

Hint: find the least common multiple of $6,7$ and $28$.