Y is the answer for four right angles
There's two ways, you can either multiply 11 and 7 to get 77 and then divide by 2, OR, you can divide 11 by 2 and get 5.5 and multiply that by 7, hope this makes sense, if you don't understand just comment and I'll explain it more :)
There would be 138 students in 6 classes because first you'd divide 207 from 9 and get 23 then you'd multiply 23 to 6 and get 138.
Answer:
the answer is 8. just think of it as subtraction. subtract +6 from +14. then you get the answer for +14+-6.