SAT Question a67a439d: Nonlinear Equations In One Variable And Systems Of Equations In Two Variables answer and explanation with Desmos solution

Choice A is correct. The solution to a system of equations is the ordered pair $\left(x,y\right)$ that satisfies all equations in the system. It's given by the first equation in the system that $x+7=10$. Substituting $10$ for $x+7$ into the second equation yields $10^2=y$, or $y=100$. The x-coordinate of the solution to the system of equations can be found by subtracting $7$ from both sides of the equation $x+7=10$, which yields $x=3$. Therefore, the ordered pair $\left(3,100\right)$ is a solution to the given system of equations.