Suppose 100 is a young monk, then eat 25 steamed buns.

100-25=75 (piece)

If they are all young monks, there will be 75 more steamed buns.

75÷ (4-1÷ 4) = 75÷15/4 = 20 (a) ...

A big monk eats (4- 1÷4) fewer steamed buns than a little monk, so there are 20 big monks.

100-20=80 (a) ... Little monk

A: There are 20 big monks and 80 little monks.