The order in which you add/subtract terms is not really important. Just make sure that what you do to one side, you do to both. You're goal is to get all the variables on one side and all of the numbers (constants) on the other. If you had added the 2 first and then dealt with the -4x, you would...

A trick to remember this is that of all the segments that you are learning (perpendicular bisector, angle bisector, medians, altitudes), perpendicular bisector has the most C's in it. Therefore, it corresponds with the point of concurrency with the most C's- Circumcenter.
Also, if you draw the...

I would start this problem by taking care of the exponents on the outside of the parentheses.
Looking at just the numerator (top) of the fraction you have (2ab^-2c^-4)^-5. When you raise an exponent to an exponent, you multiply them. Keep in mind your rules for multiplying negatives. So you...