We are given the equality
[tex]g=\frac{1+2a}{a}[/tex]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
[tex]a\cdot g=1+2a[/tex]Now, we subtract 2a from both sides. We get
[tex]a\cdot g-2a=1[/tex]We can factor on the left side a as a common factor, so we get
[tex]a\cdot(g-2)=1[/tex]Finally, we divide by (g-2) on both sides, so we get
[tex]a=\frac{1}{g-2}[/tex]