Final answer:
The function F(8)=3z+9 is provided, but no specific question related to it is asked, making it impossible to provide a solution without further context. Relevant information seems to imply we could solve for z, but this is conjecture without direct instruction.
Step-by-step explanation:
The question appears to be incorrectly written or involves an error; the function F(8)=3z+9 is provided, but the task is unclear as no specific question is formed using this function. To find a value using the function, we would typically need to substitute a value for z or be given an equation where we could solve for z. However, without further clarification or a specific question related to the function F(8), we cannot provide a solution.
Relevant information provided, such as 13 z = 2.78 or 23 z = -1.67, implies that if these are to be used in conjunction with the function F(8), we could solve for specific instances of the function. For example, using 13 z = 2.78, we could divide both sides by 13 to get the value of z and then plug that value into the function to get the result. Nevertheless, this is conjecture without a direct question referring to these pieces of information.