SAT Question cee5b352: Linear Functions answer and explanation with Desmos solution

Choice D is correct. It's given that the length of the whale was $162$ cm when it was born and that its length increased an average of $4.8$ cm per month for the first $12$ months after it was born. Since $x$ represents the number of months after the whale was born, the total increase in the whale's length, in $\text{cm}$, is $4.8$ times $x$, or $4.8x$. The length of the whale $y$, in $\text{cm}$, can be found by adding the whale's length at birth, $162$ cm, to the total increase in length, $4.8x$ cm. Therefore, the equation that best represents this situation is $y=4.8x+162$.