Hi there!
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I believe your answer is:
[tex]f(24)=4[/tex]
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Here’s why:
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[tex]f(x)=\frac{1}{4}(x-8)\\-----------\\\rightarrow f(24)= \frac{1}{4}(24-8)\\\\\rightarrow f(24) = \frac{1}{4}( 16)\\\\\rightarrow\boxed{f(24)=4}[/tex]
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Hope this helps you. I apologize if it’s incorrect.