0 is the middle number between negative numbers and positive numbers. Since 1/2 is positive, we know that 1/2 is greater than 0.
I like to reduce everything by half if I don't already know the answer.

It just so happens that is the reduced fraction.
All I did was halve 18, which is 9, and halve 34, which is 17.
Your answer would be -11.
It’s the first one -13–16