Answer
Yes, the function $f(x)=\frac{x+3}{5}$ is a linear function.
Work Step by Step
The function given is linear because of the fact that it has a constant slope. It may be written in a different form rather than $y=mx+b$, but it has a slope of $\frac{1}{5}$ for $x$ ($x$ has a coefficient of $1$, therefore, the slope is $\frac{1}{5}$. Your $b$ in the function is $\frac{3}{5}$.
