Hello there!
Sense this is a 360 degree angle, it is divide by 2. This would then be considered 180. If you (noticed) on the other side, it shows us that . . .

We then do (180-19)
You never gave a question therefore there is no answer without a question
Answer: C.
There are 215 total students in the band.
There are 27 seniors in the band.
The probability is found by dividing the number of seniors in the band by the TOTAL number of students in the band.
P(S|B) = 27/215 = 0.1255813953
You have to round off the answer too the nearest tenth.
P(S|B) = 0.13
Your answer for the greatest common factor is 6
I think the answer is 66. But I'm not sure just try and see...!