Arcs are just sections of the circle
so lets say you had a pizza
and you put some points on the crust, the legnth of the crust from point to point is that arc
example
if you put poins A and B, then arc AB is the crust between points A and B
arcs can include other points as well
and arc AB=arc BA
so
I wil name easy arcs first
arc AB
arc BC
arc CD
ard DA
now ones that include others
arc AC
arc BD
so the arcs you might want to list are
arc AB
arc BC
arc CD
ard DA
arc AC
arc DB
7. (4,5) 8. (5,-3) hope that helps
I have an expression

floating around in my head; let's see if it makes sense.
The variance of binary valued random variable b that comes up 1 with probability p (so has mean p) is

That's for an individual sample. For the observed average we divide by n, and for the standard deviation we take the square root:

Plugging in the numbers,

One standard deviation of the average is almost 2% so a 27% outcome was 3/1.9 = 1.6 standard deviations from the mean, corresponding to a two sided probability of a bit bigger than 10% of happening by chance.
So this is borderline suspect; most surveys will include a two sigma margin of error, say plus or minus 4 percent here, and the results were within those bounds.