Question

Form the intersection for the following sets.

Answer 1

The intersection of two sets is the set composed by the elements that the two sets have in common.

So, we have

$X\cap Y = \{100,\ 1000\}$

In this particular case, since Y is a subset of X, we have

$X\cap Y=Y$

In fact, all elements of Y are elements of X as well, so in particular they are common elements.