So. Conductors are people who get the money from passengers. But
this is not important.(it's their profession).
You know that more than P% of people living in our city are
conductors.
At this time, not less than Q% people do the same job.
There just can't more or less percentage of people with this job.
Now you should find the minimal possible quantity of people doing
this job, such that, of course, no number of people was not positive
integer, i.e. you should find the least number such that P% of it is
a natural number and Q% of it is also a natural number.
I think now it's understandable.
  Good Luck!