We are given the equality

and told to solve for a. That is, we should apply mathematical operations on both sides of the equality so we "isolate" variable a on one side of the equality. We start by multiplying both sides by a, so we get
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Now, we subtract 2a from both sides. We get
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We can factor on the left side a as a common factor, so we get

Finally, we divide by (g-2) on both sides, so we get
