So to solve for a, we must first get a on one side by itself. So let's add 9 to both sides to get:
[tex] Z+9=9a-3b [/tex]
Then we are going to add 3b to both sides to get the a term by itself:
[tex] Z+9+3b=9a [/tex]
And then since a has a coefficient of 9, we are going to divide by 9 to complete the solving for a:
[tex] (\frac{Z+9+3b}{9})=a [/tex]
