Question 794761
Thining about this carefully and drawing a picture, you should be able to tell that {distance of floor to cieling}={distance from top shelf to cieling}+{distance from floor to top shelf}.


Shown as values, using L for the distance from floor to top shelf,
{{{9=2&4/12+L}}}


Find L.
That all should give you a very strong start.  Now, how many equal increments of distance are between the shelves, INCLUDING the floor as an extra shelf?   Think!  There are FOUR distance increments.  


Distance between shelves is {{{highlight(L/4)}}}.