An hour is 60 mins long. 30 mins is half of it. If we take 12 miles in an hour, divide it by 2, it will be 6 miles in 30 mins, and if we take 8 miles, divide it by 2, it would be 4 miles in 30 mins. Since the questions telling us how far apart are north cyclists, we’re adding 6 and 4 to get 10 miles. In conclusion, both cyclists are 10 miles apart. I might be wrong, but that’s the best I can do.