To find the missing denominator in the expression \( \frac{3}{5} - \frac{1}{?} \), we need to ensure that both fractions have a common denominator.
Let's assign the missing denominator the variable \( x \). To perform the subtraction, we can write it as:
\[ \frac{3}{5} - \frac{1}{x} \]
To subtract these fractions, we need a common denominator. The common denominator will be the least common multiple (LCM) of the denominators 5 and \( x \).
In general, for the subtraction to be possible and meaningful, you could choose \( x \) to be any number so long as you can express the subtraction equivalently with a common denominator. If we want to simplify it to a specific term, we can set \( x = 5 \) to keep the denominators the same.
However, if we want to complete the expression accurately, any number for \( x \) would suffice as long as it provides a true mathematical operation, which indicates one type of acceptable answer.
Thus, if you want the simplest answer, you can write the missing denominator as:
\[ x = 5 \]
So the answer you could provide is:
\[ 5 \]