To model the equation \(-x + 40 = x\), we need a situation where a certain quantity (let's say money, temperature, or elevation) is balanced out by an opposite quantity plus an additional amount—in this case, 40.
Option 1: "If Alex gained as much money as she lost, she would have 40 dollars."
This suggests that her losses can be expressed as \(-x\) and her current total (40 dollars) can be modeled as \(40 - x = x\).
Option 2: "The amount of money a stock lost in the stock market was $40 more than it gained."
This suggests the loss is expressed by \(-x\) and the gain as \(x\), leading to the equation \(-x = x + 40\).
Option 3: "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."
Here, if we let \(x\) represent the days above zero, then below zero can be expressed as \(-x + 40\), leading to the equation \(-x + 40 = x\).
Option 4: "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."
Let’s assume Marsha's depth is \(-x\) feet below sea level and to equalize this, she would require \(x + 40\), leading to the equation.
Among these options, the third scenario about temperature best represents the given equation. Thus,
The best response is:
"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."