Question

if an office of 36 typist uses 12 dozen envelopes per day how many dozen envelope would an office of 125 typists of use?

Answer 1

Assuming the envelope consumption is proportional to the number of typists, you have ...
  (12 dz)/36 = x/125
  125*(12 dz)/36 = x = 41 2/3

An office of 125 typists would use 41 2/3 dozen envelopes per day.