Answer:
z = 1/81
Explanation:
The spacing is quite ambigious but I'll assume you meant: 20 = -16 + 4/9z.
Start by isolating the term that contains z by adding 16 to both sides.
20 + 16 = -16 + 16 + 4/9z.
Simplify that.
36 = 4/9z.
Now, further isolate z as a variable attached to its factor since z is in the denominator, which makes is the divisor, and therefore is not multiplied by 4/9.
36 • 9z = 4.
Continue simplifying.
324z = 4.
Now fully isolate z by dividing by 324 on both sides.
z = 4/324 = 1/81.