Answer:
Hello,
f(x)=2x-1
Step-by-step explanation:
[tex]f(x+3)=2x+5\\\\Let\ say\ x=y-3\\\\f(y-3+3)=2(y-3)+5\\\\\\f(y)=2y-6+5\\\\f(y)=2y-1\\\\\boxed{f(x)=2x-1}\\[/tex]