SAT Question 284303f1: Percentages answer and explanation with Desmos solution

Choice B is correct. It's given that there are $250$ trees in a park and of these trees, $6\%$ are birch trees. The number of birch trees in the park can be calculated by multiplying the number of trees in the park by $\frac{6}{100}$. Therefore, the number of birch trees in the park is $250\left(\frac{6}{100}\right)$, or $15$.