1. The problem is to find a number that can be used once and has four stars on each side, with the stars being equal in number on both sides. 2. Let's denote the number as $x$ and the stars as $*$. The condition is that there are four stars on each side of $x$, and the stars on the left and right must be equal. 3. This means the expression looks like this: $$****x****$$ where each $*$ represents one star. 4. Since the stars on both sides are equal and there are four stars on each side, the condition is satisfied by any number $x$ placed between four stars on each side. 5. Therefore, the number $x$ can be any number, and the stars on each side are equal in number (four stars). Final answer: Any number $x$ with four stars on each side, i.e., $$****x****$$.