All you need to do is point out that the argument reverses.
Here's the thing proved in symbols:
Intersection of Power Sets - ProofWiki
Power set of (A intersect B)=Power set of A intersect the power set of B
x is an element of D which is an element of the power set of (A intersect B). a subset of A and B must contain elements that are in both A and B so x must be an element of A and B. Since x is an element of A it must be contained in the power set of A and since x is in B it must also be in the power set of B
i think this wrong but im not sure how to fix it
Note the given wiki proof more carefully. Although x is an element of A intersection B, it is not an element of the power set of either nor their intersection. It is an element of a subset of the power set, yes, but not an element of the power set itself. A power set is a set containing all possible subsets of a given set. This really is confusing though, I know. The same concept can be applied in reverse in that although x is an element of the power set of a set, it is not an element of the set itself.