If X=8n−7n−1,n∈N and y={49n−49,n∈N} then
X⊂Y
Y⊂X
X=Y
X∩Y=ϕ
X=8n−7n−1,n∈N={0,49,490,…}Y={49n−49,n∈N}={0,49,98,147,…}
Clearly, every element of X is in Y but every element of Y is not in X.
∴ X⊂Y