SAT Question be9cb6a2: Linear Functions answer and explanation with Desmos solution

Choice D is correct. It's given that the cost of renting a backhoe for up to $10$ days is $$270$ for the first day and $$135$ for each additional day. Therefore, the cost $y$, in dollars, for $x$ days, where $x\le 10$, is the sum of the cost for the first day, $$270$, and the cost for the additional $x-1$ days, $$135\left(x-1\right)$. It follows that $y=270+135\left(x-1\right)$, which is equivalent to $y=270+135x-135$, or $y=135x+135$.