You want to solve for 'z'.
First combine like terms on either side of the equal sign.
Left side: 9z +2 ----> No like terms, leave alone
Right side: 6z - 10 -z - 4 ----> circle like terms and add
6z -z = 5z
-10 -4 = -14
Now the equation is:
9z + 2 = 5z - 14
Get all the 'z' terms on the left side and all the numbers on right side.
You can move a term to the other side if you flip the sign.
Move 5z to left side, flip the sign to -5z
Move '2' to right side, flip the sign to -2
9z - 5z = -2 -14
Add like terms
4z = -16
Divide by 4 on both sides
z = -4