SAT Question ce940f80: Nonlinear Equations In One Variable And Systems Of Equations In Two Variables answer and explanation with Desmos solution

Choice B is correct. Multiplying the left- and right-hand sides of the given equation by $25$ yields $x^2=900$. Taking the square root of the left- and right-hand sides of this equation yields $x=30$ or $x=-30$. Of these two solutions, only $30$ is given as a choice.