Let's walk through Angie's solution step by step:
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She starts with the equation: \[ -x + 7 = -11 \]
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Angie subtracts 7 from both sides: \[ -x + 7 - 7 = -11 - 7 \] This simplifies to: \[ -x = -18 \] At this point, her operation is correct.
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Next, she needs to isolate \(x\). To do this, she should multiply both sides of the equation by -1: \[ x = 18 \]
Instead, Angie did not perform the last step correctly because she incorrectly left \( -x = -18 \) and stated \( x = -18 \). The error occurred when she concluded that \( x = -18 \).
The correct solution is: \[ x = 18 \]
So, Angie made an error in the final step of her solution.