3/8 of 800 is 300.. 3/8 of 800 is really 300.To check, take 3/8 and convert it to .375. Then, find what .375 of 800 is... 300!
Also, you can see that 3/8 and 800 can easily be converted to a common denominator... 800. So, just add 2 zeros to 3, and you get 300!