SAT Question 8c98c834: Linear Equations In Two Variables answer and explanation with Desmos solution

Choice B is correct. It's given that the equation $y=0.1x$ models the relationship between the number of different pieces of music a certain pianist practices, $y$, and the number of minutes in a practice session, $x$. Since it's given that the session lasted $30$ minutes, the number of pieces the pianist practiced can be found by substituting $30$ for $x$ in the given equation, which yields $y=0.1\times 30$, or $y=3$.