Explain step by step =) harry rides his bike 25 3/8 miles. karen rides her bike 25 2/5 miles. who rides farther?

To answer this question we need to use subtraction. 
we need to make the denominators the same. 
In order to make them the same we need to find the least common multiple, of 8 and 5. 
The least common multiple(the smallest shared value of the two numbers) is 40. 

Next we divide our old denominator 5 by 40, which gives us 8, we multiply 8 by the numerator 2, which gives us 16. So now we have 16/20. We have to do the same to the other side. 8÷40 = 5.  5 x 3 = 15. Now we have 15/20.

Now we have a brand new equation, 16/40 - 15/40. The answer is 1/40. 
In a fraction the answer is 1/40, so Karen rides her bike further. 

In decimal form the answer is 0.025. 

I hope this helps!