SAT Question 1dcea480: Probability And Conditional Probability answer and explanation with Desmos solution

Choice A is correct. Multiplying the number of marbles in the bag by the probability of selecting a blue marble gives the number of blue marbles in the bag. Since the bag contains a total of $60$ marbles and the probability that a blue marble will be selected from the bag is $0.35$, there are a total of $0.35\times 60=21$ blue marbles in the bag.