Z= 3(-4-a)/4(4n+3p)
Multiply z by the denominator of the function to start to get things all on one side.
Z(4(4n+3p)=3(-4-a)
Divide by 3 to remove the parentheses from the right side.
4Z(4n+3p)/3=-4-a
Add four to both sides to remove it from the right.
4Z(4n+3p)+4/3=-a
Multiply by -1 to get a all by itself.
-4Z(4n+3p)+4/3=a