For #1.

Reflexive: is it true that x-x=0 for all x? If so, the relation is reflexive.

Symmetric: is it true that if x-y=0 then y-x=0? If so, the relation is Symmetric.

Transitive: is it true that if x-y=0 & y-z=0 then x=z=0? If so the relation is transitive.

Do note that x-y=0 if and only if x=y.