Idon't get how to do the number 8 (a, b,c) can someone me explain

For A and B, let's not pay attention to the north and south thing, since the miles they traveled aren't affected by directions (try imagining traveling 15 miles, is it affected by the direction?). Since they came from the same house,
A. Jack is 15 miles from his home
B. Alex is 10 miles from his home

C is a bit trickier, because you have to use the directions now. I'd suggest getting graph paper to draw it out, or just drawing a graph yourself. Since north and south are opposite from each other, you just add the miles they traveled together.
C. Jack is 25 miles away from Alex

I hope this helps!