You have to find the amount of distance they traveled since the start of the journey. 3/5 + 3/8 is 39/40. How did we get that, you may ask?
We need to find a number that both 5 and 8 have to make. That can be 40. But how we made 5 and 8 40, we need to do the same to the top numbers. So 39/40 when we add them up. Finally, we need to substract that from the whole, and this gets you 1/40. Hope this helps.
