SAT Question fbb0ea7f: Linear Equations In One Variable answer and explanation with Desmos solution

Choice A is correct. It's given that the rocket contained $467,000$ kilograms (kg) of propellant before launch and had $362,105$ kg remaining exactly $21$ seconds after launch. Finding the difference between the amount, in $\text{kg}$, of propellant before launch and the remaining amount, in $\text{kg}$, of propellant after launch gives the amount, in $\text{kg}$, of propellant burned during the $21$ seconds: $467,000-362,105=104,895$. Dividing the amount of propellant burned by the number of seconds yields $\frac{104,895}{21}=4,995$. Thus, an average of $4,995$ kg of propellant burned each second after launch.