Final answer:
Lucita's mistake was underestimating the answer. The estimated answer of -3 is much lower than the actual result of -0.026.
Step-by-step explanation:
Lucita's mistake was that she estimated the answer to be -3, which is too low. When she did the division problem 3.302 ÷ -1.27, she got -0.026 as the result.
In this problem, Lucita is dividing a positive number by a negative number, which means the result will be negative. The estimated answer of -3 is incorrect because it is much lower than the actual result of -0.026. Lucita's mistake was underestimating the answer.