A-2=-2
Add 2 to both sides to isolate and solve for a
A=0
A rule of exponents is if 0 is raised to any positive power it is 0. If it is raised to a negative power it is undefined (I will explain at the end of this.) since we know a is 0 and 0 to the power of 2 is 0 the answer it his question is 0.
Here I explain why 0 raised to a negative power is undefined.
For example 0 to the -2 power is the same as 1/0^2 (raising a number to the negative power is the same as raising the same numbers reciprocal to the positive power). 1/0^2=1/0 which is undefined. This applies for any negative power to 0.