Let $a,b,c,d$ be real numbers such that $a<b < c<d$. Express the set $[a,b] \cup [c,d]$ as the difference of two sets

Question

I am not sure how I would express these sets as a difference. My original attempt was to show that it is the set $[a,d]$ and take away the universal set. I would appreciate any help. Thank you in advance.

Answer 1

As suggested in the comments, you can take $$[a,d]-(b,c).$$ This basically takes all the numbers from $a$ to $d$, including the two, and then removes the numbers from $b$ to $c$, not including $b$ and $c$.

Answer 2

Universal set is too big to be taken away.Try this-

$$[a,d]-(b,c)$$