1. The problem is to solve for number 15 (assuming the problem is solving the number 15 or an equation involving 15). 2. Since the problem statement isn't explicit, if we treat it as solving for $x$ in $x = 15$, then the solution is straightforward. 3. Thus, $x = 15$. 4. If the problem was to solve an equation given number 15, please clarify the exact equation or context. 5. Without additional info, the final answer is $15$.