# Regular expression of 011=110 in string

What is the regular expression for language containg no. of 011 equal to 110 in string ?

Usually, languages of the form "The number of $x$s is equal to the number of $y$s" aren't regular because you could have an arbitrarily long sequence of $x$s with no $y$s but a finite state automaton can't remember how long that sequence was.
However, in this case, any time you see $011$, either the rest of the string contains only $1$s or the string looks like $0111^k0\ldots$ for some $k\geq 0$ and you've found the matching $110$. If you think about this for a bit, and try some examples, you should be able to figure out some simple rules that determine whether a string is in the language, and then implement that as a regular expression.