To model the equation \(-x + 40 = x\), we can interpret the variables in context. Here, \(x\) represents the amount of money lost (which is negative), and \(-x\) would thereby represent the amount gained. The equation takes the form of stating that the amount lost, when increased by $40, equals the amount gained.
Among the provided responses, the appropriate real-world problem that best captures this scenario is:
The amount of money a stock lost in the stock market was $40 more than it gained.
This statement aligns with the equation since it implies that the negative loss (represented by \(-x\)) plus $40 equals the amount gained (represented by \(x\)).