SAT Question 79137c1b: Two-variable Data Models And Scatterplots answer and explanation with Desmos solution

Choice B is correct. From the shape of the cluster of points, the line of best fit should pass roughly through the points $(1,200)$ and $(2.5,350)$. Therefore, these two points can be used to find an approximate equation for the line of best fit. The slope of this line of best fit is therefore $\frac{y_2-y_1}{x_2-x_1}=\frac{350-200}{2.5-1}$, or $100$. The equation for the line of best fit, in slope-intercept form, is $y=100x+b$ for some value of $b$. Using the point $(1,200)$, $1$ can be substituted for $x$ and $200$ can be substituted for $y$: $200=100\times 1+b$, or $b=100$. Substituting this value into the slope-intercept form of the equation gives $y=100x+100$.