The expression you provided appears to be related to the square root operation. Given \(81 + | = 9\), we can interpret it as follows:
The square root of the number inside the box plus 81 equals 9:
\[
\sqrt{81 + x} = 9
\]
Squaring both sides, we eliminate the square root:
\[
81 + x = 9^2
\]
\[
81 + x = 81
\]
Now, subtract \(81\) from both sides:
\[
x = 81 - 81
\]
\[
x = 0
\]
However, it seems there's a misunderstanding in my interpretation. Let’s analyze a simpler mathematical relationship that involves the given options. If we take the equation as simply adding \(81\) with the figure in the box to get \(9\), that wouldn’t hold true as \(81\) is already greater than \(9\).
There seems to be a possibility of evaluating \(| = x\) as the absolute value function, but we don't require that here due to the context and lack of additional expressions.
Given the typical operation and available answers, none fit the straightforward interpretation. Thus, the correct interpretation that fits best contextually involves plugging in values for completeness:
Testing the other values quickly shows none hold for:
- A: \(81 + 9 = 90\) (wrong)
- B: \(81 + 90 = 171\) (wrong)
- C: \(81 + 72 = 153\) (wrong)
- D: \(81 + 10 = 91\) (wrong)
Thus it might require clarification of the initial problem setup because ( | or boxed representations require further context in actual mathematical situations.
The only option that can fit as originally detailed but in a different format could be \( \text{absolute value surroundings.}\)
If you can clarify further surrounding the box or operational expectations, please share, and I’d be happy to assist better!