There is no proposition if Y≠X, then X≠0, Y≠0.
Negative proposition if X≠0, Y≠0, then y ≠ x.
If XY=6, then X=3 and Y=2. If X=3 or Y=2, then XY=6.
There is no proposition if XY≠6, then X≠3 or Y≠2.
If the negative proposition is X≠3 or Y≠2, then XY≠6.
No proposition or proposition and no proposition.
The no proposition of a proposition is a yes or no proposition.
I hope it helps you.