In general, this kind of equation, with one term a constant times the variable and another term with the variable in an exponent, can't be solved algebraically; you need to use a graphing calculator, or calculus or some other numerical method.
But this particular problem can be solved easily, because the answer is "nice".
We can tell that the equation will have a "nice" answer only if the value of the variable is an integer; if not, we would not be able to evaluate 2^(x-2) exactly.
So simply try small integer values for x to find the answer.
x x-2 8x 2^(x-2)
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3 1 24 2
4 2 32 4
5 3 40 8
6 4 48 16
7 5 56 32
8 6 64 64
ANSWER: x=8