SAT Question a94ed4e0: Systems of Linear Equations answer and explanation with Desmos solution

Choice D is correct. Adding the second equation to the first equation in the given system of equations yields $3y-3y=4x+9x+17-23$, or $0=13x-6$. Adding $6$ to each side of this equation yields $6=13x$. Multiplying each side of this equation by $3$ yields $18=39x$. Therefore, the value of $39x$ is $18$.