Website A:
c = 10 + 0.25 s
where c is the cost and s is the number of songs.
Website B:
c = 0.75 s
The equation ( answer ):
10 + 0.25 s = 0.75 s
We can solve this equation:
10 = 0.5 s
s = 10 : 0.5
s = 20 ( Marvin would have to buy 20 songs to to make the costs equal )
In the terms you used, not unless you want an integer for an answer.
The formula for the equation of a circle is:
(x - h)^2 + (y - k)^2 = r^2
(h, k) is the center.
So the equation would be:
(x + 2)^2 + (y - 3)^2 = 5^2
or
(x + 2)^2 + (y - 3)^2 = 25