The answer is 0.135
Using the calculator, e^-2 = 0.13533528323
Since we want to round it to three decimal places, we are interested in the 3rd and the 4th decimal places. If the 4th decimal place is bigger than 5, we should increase the 3rd decimal place by 1. If it is smaller than 5, then the 3rd decimal place remains the same. In our case, the 4th decimal place is 3, which is smaller than 5, therefore, the 3rd decimal place will remain the same:
e^-2 = 0.135