Find the Missing Operator in 99?99 = 0: Mathematical Symbol Problem

To solve this problem, let's test each of the given operators with the number 99 to verify which one results in 0:

• $99 + 99$: This equals $198$, not $0$.
• $99 \times 99$: This equals $9801$, not $0$.
• $99 - 99$: This operation results in $0$, which matches our expectation.
• $99 : 99$: Assuming ':' represents division, $99 : 99$ equals $1$, not $0$.

Therefore, the operation that satisfies the equation $99 ? 99 = 0$ is subtraction.

Hence, the correct choice is: $-$.