Agroup of hikers walked 8 7/10 miles to caribou cave and then 5 1/5 miles to silver stream how far did they walk altogether

So we are going to take of the whole numbers, 8 and 5, and add them together.
8 + 5 = 13
Now we are going to add the fractions. So, as you can see the bottom numbers are different, and they have to be the same. The easiest way to make them the same is to double 1/5. so the bottom is 10, but we can't just double the bottom, the top has to double if the bottom doubled. So we get 2/10. Now that the bottoms are the same, we can add them easy.
7/10 + 2/10 = ???
Add the numerators.
7 + 2 = 9
Then we would add the denominators, but because we are doing addition and they are the same, the bottom stays 10. So we put the new numerator on top of our denominator. 
So the answer is 9/10, and this cannot be simplified.

13 9/10
1/5 ×2=2/10
2/10+7/10=9/10
then, you add8+5 to get 13
combine 13 and 9/10 (13 9/10) and thats your answer!

C. c is the correct answer.