The answer is 18.2
I got the answer by solving it
Start by proving to them that the number 0.57 can be converted into a fraction . A whole number can't exactly be put in to a fraction. 0.57 can be converted to 14.25/25. This information means that 0.57 IS a rational number. Hope this convinced them!
The answer is
-5/8+9/2=3 7/8 or 31/8
so you should put 31 in the green box
