SAT Question d909cd31: Systems of Linear Equations answer and explanation with Desmos solution

Choice C is correct. It's given that the system has infinitely many solutions. A system of two linear equations has infinitely many solutions when the two linear equations are equivalent. Dividing both sides of the given equation by $5$ yields $-3x+5y=13$. Dividing both sides of choice C by $4$ also yields $-3x+5y=13$, so choice C is equivalent to the given equation. Thus, choice C could be the second equation in the system.