This is equal to:
When you add a negative number, it turns into subtraction.
First, I would change it to mixed numbers:
Now, you need to change the denominators to make sure they are the same on both fractions. I changed the first fraction's denominator to 4 so they match. You can do this by multiplying the numerator by 2:
Now, you simply subtract:
10-9=1
1/4 is your answer.
I hope this helps :)