What is 11.375 in faction

11 3/8 would be the simplified version and 91/8 would be the other way.

The answer would be: 11 and 3/8
Here's how:
So, look at the 11. That is the whole number, so don't worry about it for now. Now look at the '375' part. That has to change. So think about it, the 375 is in the thousandths place. So put 375 over 1000 (375/1000). You can simplify that by 5. So it would equal: 75/200. But look, you can simplify again. (by 5) That would equal: 15/40. Again, simplify by 5: 3/8. Now look! You got that part done. Now put the 11 and 3/8 together, so the answer would be 11 and 3/8. 
Good luck and hope I helped! :) Follow if you want.