SAT Question e438ec3f: Probability And Conditional Probability answer and explanation with Desmos solution

Choice C is correct. If a tree from one of these rows is selected at random, the probability of selecting a maple tree, given that the tree is $20$ feet or taller, is equal to the number of maple trees that are $20$ feet or taller divided by the total number of trees that are $20$ feet or taller. It's given that there are $6$ rows of birch trees, and each row of birch trees has $8$ trees that are $20$ feet or taller. This means that there are a total of $6\left(8\right)$, or $48$, birch trees that are $20$ feet or taller. It's given that there are $5$ rows of maple trees, and each row of maple trees has $9$ trees that are $20$ feet or taller. This means that there are a total of $5\left(9\right)$, or $45$, maple trees that are $20$ feet or taller. It follows that there are a total of $48+45$, or $93$, trees that are $20$ feet or taller. Therefore, the probability of selecting a maple tree, given that the tree is $20$ feet or taller, is $\frac{45}{93}$, or $\frac{15}{31}$.