as you already know, to get the inverse of any expression, we start off by doing a quick switcharoo on the variables, and then solve for "y", so let's do so,
[tex]\bf \stackrel{f(x)}{y}=\cfrac{x-5}{3}\qquad inverse\implies \boxed{x}=\cfrac{\boxed{y}-5}{3}
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3x=y-5\implies 3x+5=\stackrel{f^{-1}(x)}{y}\\\\
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3(3)+5=f^{-1}(3)\implies 14=f^{-1}(3)[/tex]
