what is 25% of 25% of 25% of 400

(0.25)(400) = 100

(0.25)(100) = 25

(0.25)(25) = 6.25

etc.

Note that 25% = .25   and "of" means "multiply"

So

(.25) x (.25) x (.25) x 400  =

(.25)³ x 400 =

6.25