Olá,
[tex] \tt \: y = f(x) = {x}^{2} + 3 \\ \tt \: x = 5 \\ \tt \: y = f(5) = {5}^{2} + 3 \\ \tt \: y = 25 + 3 \\ \boxed{\tt \: y = 28} \\ [/tex]
