9=7z-13z-21 please show correct step by step thank youu!

9 = 7z−13z−21
Step 1: Simplify both sides of the equation.
9 = 7z−13z−21
9 = 7z+−13z+−21
9 = (7z+−13z)+(−21)(Combine Like Terms)
9 = −6z+−219 = −6z−21

Step 2: Flip the equation.
−6z−21 = 9

Step 3: Add 21 to both sides
.−6z−21+21 = 9+21
−6z = 30

Step 4: Divide both sides by -6
.−6z/−6 = 30/−6
z = −5