SAT Question c4d49134: Linear Functions answer and explanation with Desmos solution

Choice D is correct. In the given equation, $s$ is the speed, in miles per hour, of a certain car $t$ seconds after it began to accelerate. Therefore, the speed of the car, in miles per hour, $5$ seconds after it began to accelerate can be found by substituting $5$ for $t$ in the given equation, which yields $s=40+3\left(5\right)$, or $s=55$. Thus, the speed of the car $5$ seconds after it began to accelerate is $55$ miles per hour.