Here is what it means: Perimeter = the sum of the lengths of all the sides. Apothem = a segment that joins the polygon's center to the midpoint of any side that is perpendicular to that side.
What I would do is break up into part. First do 10*10*10 which is 1,000. Then add 56 and 50 which is 106. after you do that and get 1,106 divded it by 25 which is 42.54. Hope I helped.