If the center is (0, 0), then there is no side to side or up or down motion. The center is at the origin. The standard form of a circle is (x-h)^2 + (y-k)^2 = r^2. Your h and your k are both 0's, so just fill in and square the radius:
x^2 + y^2 = 64
Yes it would be the opposite for example -12 it would be 12 and then 13 would stay 13
The equation simplified (combine like terms) would be 11x+(-24) =180.
Since adding a negative is the same as subtracting a positive, you could also write it as this: 11x-24=180. Next step is isolate the variable, so to do that you need to add 24 to both sides of the equation: 11x-24+24=180+24. This is the same as 11x=204. Now to get only one of the variable, you need to divide both sides by 11. x=18.54 repeating or x=18 6/11. Hope this helped!
Answer:

Step-by-step explanation:
7x-4=3x+ 8
-3x of both sides 4x-4=8
plus 4 to both sides 4x=12
12 divide by 4 = 3
hopeful that helps