The correct answer is C. hope this helps
Answer:
AREA:

CIRCUMFERENCE:

Step-by-step explanation:
The formula that is used to calculate the area of a circle is:

Where "r" is the radius of the circle.
The formula for calculate the circumference of a circle is:

Where "r" is the radius of the circle.
Then, you need to find the radius. This is:

Substituting the radius, you get that the area and the circumference are:
AREA:

CIRCUMFERENCE:

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.
I hope this helps for question a=16
I hope this helps for question b=12
Ok so cos(x) = sin(90-x) so using that you can get sin(7x-15) = sin(90-(3x+5)) so 7x-15 = -3x+85. 10x = 100 and x = 10. Use that to find the 2 angles are 55 and 35