The answer to this problem is 4
We know that:

is an equation of a circle.
When we substitute x and y (from the pairs we have), we'll get a system of equations:

and all we have to do is solve it for a, b and r.
There will be:

From equations (II) and (III) we have:

and from (I) and (II):

Now we can easly calculate a and b:

Finally we calculate

:

And the equation of the circle is:
The first picture would be choice answer c because the number of x's represent how many birds wings are this size. The number on the tic mark represents the size of the wing span. So you would take the number of x's times the tic mark represented under it. There are 3 birds with 3 1/8 wingspan so it wold be 3 1/8 *3. Hoped this helps for the first one!
The answer is not in the choices so ... but the (0,4), (1,1), (2,6)
Hope This Help.
Xd <3
C), cause you would subtract 5 from 53 in order to move it, and would get 6x=48. Then, you would divide by six on both sides, and the answer would be x=8, so Number C.