Answer:
D C B
Step-by-step explanation:
The answer is -12. Do you need to know how I did it?
1) a. OSL
2) i think is b. linear pair
3) d.vertical angles
To subtract fractions, you need to obtain a common denominator. We can achieve this, in this case, by multiplying:

Simplify this:

Now we have common denominators, so we can easily just subtract the numerators, and we have the answer:

Notice that this is divisible by 2:

That's your answer!