Others have commented on the (incorrect) use of 2/11 to specify the desired interval.
I personally however prefer writing things like that using ANSI interval literals which makes reading the query much easier:
sysdate - interval '2' hour
It also has the advantage of being portable, many DBMS support this. Plus I don’t have to fire up a calculator to find out how many hours the expression means – I’m pretty bad with mental arithmetics 😉