Geometry

Question Analysis
This question flips the typical probability calculation process.
Instead of finding the probability given the number of favorable and total outcomes, it requires determining the number of favorable outcomes (yellow marbles) given the probability and the total number of outcomes.
The main focus is on using the probability formula in a reverse - engineering manner.

Key Concept Explanation
The probability formula can be rearranged to solve for an unknown variable when the other values are known.

Step-by-Step Solution
We know that the total number of marbles (total number of possible outcomes) is 12, and the probability of picking a yellow marble is .
Using the formula