Question

if we say A is the subset of B and

we say B is a subset of A
then it is a one thing or these are the different things

Answer 1

this statement can be true if A=B means both sets are equal

if two sets are equal then we can say one set is subset of other and other set is sub set of first set

i hope it would help you

Answer 2

I think it's a one thing because its a rule of sets that if one set is subset of other set then the other set is also a subset of first set.