You would do 3/5 times 10 to get your answer to your problem. I think. That is what I would do anyway
first you have to get 3/5 to a decimal to make it easier to multiply. so you would do 5 times 20 and that would make your denominator 100.
if you times the denominator by 20, you have to do the same thing to the numerator so 3 times 20 is 60 so thats 60/100 which is 0.60 and thats equivalent to 3/5 and 6/10 and all that. so 0.60 times 10 is 6, so your coach runs 6 miles everyday. or you could do 10/1 times 3/5.