Answer:
3 or 4, depending on the intended meaning of [x]
Step-by-step explanation:
Perhaps you mean ...
[tex]\displaystyle f(x)= \lfloor x\rfloor -5\\\\f(8.6)=\lfloor 8.6\rfloor-5=8-5=3[/tex]
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On the other hand, perhaps you mean ...
[tex]\displaystyle f(x)=\lceil x\rceil -5\\\\f(8.6)=\lceil 8.6\rceil-5=9-5=4[/tex]
