Daria walked 1 2/5 miles this morning and 2 3/10 miles this afternoon. how many miles did daria walk in all?

The answer is 3 7/10 miles 

In all, means add up
1 2/5 + 2 3/10
rewrite into improper fractions
7/5 + 23/10
To add, you must have the same denominator
in this case, multiply the first fraction by 2 to get the denominator to 10
7*2/5*2
14/10

now solve
14/10 + 23/10
37/10

Now you can rewrite this to a mixed number
3  7/10

She walked 3  7/10 miles total of the day.

Hope this helps