To find out how many miles Kelly walks after three days, you can multiply the distance she walks each day by the number of days.
Kelly walks \( \frac{4}{5} \) of a mile each day.
So, after three days, the total distance she walks is:
\[ 3 \times \frac{4}{5} = \frac{12}{5} \]
Now, to convert \( \frac{12}{5} \) to a mixed number, divide 12 by 5:
\[ 12 \div 5 = 2 \quad \text{with a remainder of} \quad 2 \]
So, \( \frac{12}{5} = 2 \frac{2}{5} \).
Therefore, after three days, Kelly walks \( \frac{12}{5} \) miles or \( 2 \frac{2}{5} \) miles.