X2 + y2 − 4x + 12y − 20 = 0 (x − 6)2 + (y − 4)2 = 56 x2 + y2 + 6x − 8y − 10 = 0 (x − 2)2 + (y + 6)2 = 60 3x2 + 3y2 + 12x + 18y − 15 = 0 (x + 2)2 + (y + 3)2 = 18 5x2 + 5y2 − 10x + 20y − 30 = 0 (x + 1)2 + (y − 6)2 = 46 2x2 + 2y2 − 24x − 16y − 8 = 0 x2 + y2 + 2x − 12y − 9 = 0 pairs arrowboth arrowboth arrowboth arrowboth

For this case, what we must do is fill squares in all the expressions until we find the correct result.
 We have then:
 
 x2 + y2 − 4x + 12y − 20 = 0 x2 + y2  − 4x + 12y = 20
 x2  − 4x + y2 + 12y = 20
 x2  − 4x + (12/2)^2 + y2 + 12y  + (-4/2)^2 = 20 + (12/2)^2 + (-4/2)^2
 x2  − 4x + (6)^2 + y2 + 12y  + (-2)^2 = 20 + (6)^2 + (-2)^2
 x2  − 4x + 36 + y2 + 12y  + 4 = 20 + 36 + 4
 (x − 2)2 + (y + 6)2 = 60 

 3x2 + 3y2 + 12x + 18y − 15 = 0 
 x2 + y2 + 4x + 6y − 5 = 0 
 x2 + y2 + 4x + 6y  = 5 
 x2  + 4x + (4/2)^2 + y2 + 6y + (6/2)^2 = 5 + (4/2)^2 + (6/2)^2 
 x2  + 4x + (2)^2 + y2 + 6y + (3)^2 = 5 + (2)^2 + (3)^2 
 x2  + 4x + 4 + y2 + 6y + 9 = 5 + 4 + 9 
 (x + 2)2 + (y + 3)2 = 18 

 2x2 + 2y2 − 24x − 16y − 8 = 0
 x2 + y2 − 12x − 8y − 4 = 0
 x2 + y2 − 12x − 8y = 4 
 x2 − 12x + (-12/2)^2 + y2 − 8y + (-8/2)^2 = 4 + (-12/2)^2 + (-8/2)^2
 x2 − 12x + (-6)^2 + y2 − 8y + (-4)^2 = 4 + (-6)^2 + (-4)^2
 x2 − 12x + 36 + y2 − 8y + 16 = 4 + 36 + 16
 (x − 6)2 + (y − 4)2 = 56 

 x2 + y2 + 2x − 12y − 9 = 0
 x2 + y2  + 2x - 12y = 9
 x2  + 2x + y2 - 12y = 9
 x2  + 2x + (2/2)^2 + y2 - 12y  + (-12/2)^2 = 9 + (2/2)^2 + (-12/2)^2
 x2  + 2x + (1)^2 + y2 - 12y  + (-6)^2 = 9 + (1)^2 + (-6)^2
 x2  + 2x + 1 + y2 - 12y  + 36 = 9 + 1 + 36
 (x + 1)2 + (y − 6)2 = 46

Ican't do any of the other stuff, but i can get you started. the answer, i believe, is $2.50.