SAT Question 3148fe3e: Nonlinear Equations In One Variable And Systems Of Equations In Two Variables answer and explanation with Desmos solution

Choice B is correct. Adding $y$ to each side of the second equation in the given system of equations yields $8x+16=y$. Substituting $8x+16$ for $y$ in the first equation yields $x^2+8x+16+10=10$. Subtracting $10$ from each side of this equation yields $x^2+8x+16=0$. This equation can be rewritten as ${\left(x+4\right)}^2=0$. Taking the square root of each side of this equation yields $x+4=0$. Subtracting $4$ from each side of this equation yields $x=-4$. Therefore, the value of $x$ is $-4$.