To model the equation \(-x + 40 = x\) in a real-world scenario, we can analyze the given options in relation to the setup of the equation.
The equation implies that one quantity (which we can consider as the amount gained or the temperature above zero) is equal to another quantity (which we can consider as the amount lost or the temperature below zero) plus a constant (in this case, 40).
Now let's look at the responses:
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"The amount of money a stock lost in the stock market was $40 more than it gained."
- This would translate to \( \text{Loss} = \text{Gain} + 40 \), which does not match our equation.
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"If Alex gained as much money as she lost, she would have 40 dollars."
- This would indicate that \( \text{Gain} - \text{Loss} = 40 \), which does not match our equation.
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"Marsha is below sea level. To get as far above sea level as she is below, she would have to move to a location 40 feet higher."
- This represents that if Marsha needs to get to a position higher than sea level, the distance she has to move (which we can consider as \(x\)) is such that her starting point (below sea level, denoted as \(-x\)) plus 40 equals the height she must reach (which is \(x\)). This aligns with our equation.
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"The number of days that the temperature has been below zero is 40 fewer than the number of days the temperature has been above zero."
- This translates to \( \text{Days below zero} = \text{Days above zero} - 40\), which does not match our equation.
Based on this analysis, the best real-world problem that models the equation \(-x + 40 = x\) is:
Marsha is below sea level. To get as far above sea level as she is below, she would have to move to a location 40 feet higher.