Dear Carlaac04,
To answer this questions you need to know that there are 1,760 yards in a mile. Multiply that by 2 and you get 3,520 yards. Next you multiply 400 by 5, because the each track is 400 yards and Keisha walked 5 tracks, which is equal to 2,000. Lastly, you subtract 2,000 from 3,250 which is equal to 1520 yards.
First, let's convert the mixed fraction into an improper fraction (trust me, mixed fraction are pretty much the worst things to deal with, especially with higher level math):


Then, to subtract, since you need a common denominator, I would multiply the second fraction by 2 to get:

Now that we have a common denominator, we are ready to subtract:

Since that's the most simplified form, and you have been asked the question in a mixed fraction form, let's convert that to a mixed fraction. The remainder of the numerator divided by the denominator is 1, and the quotient is 3. The denominator stays the same. So, this is what results:

And that's your answer:

Hope this all makes sense. If anything doesn't, feel free to tell me!
The factor of 52 is 1, 2, 4, 13, 26, and 52