### Instruction: What is $0.8\overline{4}-0.\overline{4}$? Express your answer as a common fraction.### Response: I notice that both numbers have repeating decimals, so I want to find a way to eliminate them.
I also notice that the repeating digit is 4 in both cases, so I think that subtracting them might make things easier.
To do that, I need to align the decimals and write the numbers in a column.
I get: 0.8444... - 0.4444...
Now, I can subtract digit by digit, starting from the right.
I get: 0.4000...