Whats the sum of the quotients of 25x^2/5x and the quotients of 8x^2/x ?

25x^2/5x=5x

and

8x^2/x=8x

add the quotients: 5x + 8x = 13x 

There you go!

I think you mean the following:

"What's the sum of the quotient 25x^2/5x and the quotient 8x^2/x ?"

That would be:

25x^2        8x^2
  + 
   5x              x

Here the LCD is 5x.  Mult. numerator and denom. of the 2nd fraction by 5:

25x^2        5*8x^2
  + 
   5x              5x

25x^2        5*8x^2       (25+40)x^2
  +  = = 13x (answer)
   5x              5x                  5x

The answer is 225 miles per 4.5 hours. hope this ; )