SAT Question 4aaa9c42: Percentages answer and explanation with Desmos solution

Choice D is correct. It's given that $a$ is $2,241\%$ of the sum of $b$ and $c$. This can be represented by the equation $a=\left(\frac{2,241}{100}\right)\left(b+c\right)$, or $a=22.41\left(b+c\right)$. It's also given that that $b$ is $83\%$ of $c$. This can be represented by the equation $b=\left(\frac{83}{100}\right)c$, or $b=0.83c$. Dividing both sides of this equation by $0.83$ yields $\frac{b}{0.83}=c$. Substituting $\frac{b}{0.83}$ for $c$ in the equation $a=22.41\left(b+c\right)$ yields $a=22.41\left(b+\frac{b}{0.83}\right)$, or $a=22.41\left(\frac{1.83b}{0.83}\right)$, which is equivalent to $a=\frac{41.0103b}{0.83}$, or $a=49.41b$. This equation is equivalent to $a=\left(\frac{4,941}{100}\right)b$; therefore, $a$ is $4,941\%$ of $b$.