In order to evaluate the value of the expression "r + 4" at r = 13, we just need to use the value of r equal to 13 in the expression and then calculate the final value.
So we have that:
[tex]\begin{gathered} r+4 \\ =13+4 \\ =17 \end{gathered}[/tex]So the value of "r + 4" at r = 13 is 17.
