It is not so easy as it seems at first, but if you could separate all symbols and all numbers (I think this is the most difficult part of this task) - you'll get success!
Some tests:
IN:
-2008/2009
-
-2008/2009
OUT: 0

IN:
8/9
*
9/4
OUT: 2

IN:
7/10
/
-10/7
OUT: -49/100

IN:
1 1/3
+
3 5/6
OUT: 5 1/6