To solve the equation \( X - n = ____ \), where \( X \neq 0 \) and \( n \) is a counting number, you can rearrange the equation to find the answer:
\[ X - n = X + (-n) \]
So, the blank can be filled with \( X - n \), or you can also express it as \( X + (-n) \).
If you're looking for a specific answer based on a particular value of \( X \) and \( n \), you would simply subtract \( n \) from \( X \). For example, if \( X = 5 \) and \( n = 2 \):
\[ 5 - 2 = 3 \]
Thus, the answer may vary depending on the values of \( X \) and \( n \). If you can provide specific values for \( X \) and \( n \), I can give you a specific answer.