Answer:
60 students
Step-by-step explanation:
The confidence interval of a proportion is given by:

Where 'p' is the proportion of students who responded 'yes', 'z' is the z-score for a 95% confidence interval (which is known to be 1.960), and 'n' is the number of students in the sample.
If the confidence interval is from 0.584 to 0.816, then:

60 students were in the sample.
The area of a circle if the diameter is 80 is
A=5026.55
-3x -3y = -12
3x + 6y = -6
3y = -18
y = -6
x - 6 = 4
x= 10