If I did everything correctly, It should be DEF.
Hope you get an A :d
The "I"'s r variables, now u do 2-5 which sequels -2. now u do 4+7 and that ='s 11. now I think u take 11 and -2 and u subtract 11-(-2). or it could be change the negative into a positive and add them together.
I believe the answer is the last option choice.
Answer : 6 is opposite of 1