Question 331718
This is just a matter of finding the LCM of 12,16, and 18

That is, the smallest number that all three numbers will divide into.

How about 144?.

144/16=9
144/12=12
144/18=8

They all pass the starting point at the same time in 144 minutes.

How to find the LCM of three numbers?:

Factor each number:

{{{12=2^2*3}}}

{{{16=2^4}}}

{{{18=2*3^2}}}

Now, take the largest power of each factor that appears in all three.

The highest two power is 2^4 and the largest 3 power is 3^2

Multiply them and we get (2^4)(3^2)=16*9=144.