SAT Question 369b7bb7: Nonlinear Functions answer and explanation with Desmos solution

Choice C is correct. It's given that the function $g$ is defined by $g\left(x\right)=\sqrt{8x+1}$. Substituting $3$ for $x$ in the given function yields $g\left(3\right)=\sqrt{8\left(3\right)+1}$, which is equivalent to $g\left(3\right)=\sqrt{25}$, or $g\left(3\right)=5$. Therefore, the value of $g\left(3\right)$ is $5$.