SAT Question b5ebd31c: Nonlinear Equations In One Variable And Systems Of Equations In Two Variables answer and explanation with Desmos solution

Choice B is correct. Subtracting $t$ from each side of the given equation yields $2r-t=9s$. Dividing each side of this equation by $9$ yields $\frac{2r-t}{9}=s$, which can be rewritten as $s=\frac{2r-t}{9}$. Therefore, the equation $s=\frac{2r-t}{9}$ correctly expresses $s$ in terms of $r$ and $t$.