To calculate the probability of picking a yellow marble from Felix's bag, we need to know the total number of marbles and how many of those marbles are yellow.
Felix has:
- 6 yellow marbles
- 6 green marbles
The total number of marbles is: \[ 6 \text{ (yellow)} + 6 \text{ (green)} = 12 \text{ marbles} \]
The probability of picking a yellow marble (P(Yellow)) is given by the ratio of the number of yellow marbles to the total number of marbles:
\[ P(\text{Yellow}) = \frac{\text{Number of Yellow Marbles}}{\text{Total Number of Marbles}} = \frac{6}{12} = \frac{1}{2} \]
This probability remains constant regardless of the number of times Felix picks a marble because he replaces the marble each time. Thus, the probability of picking a yellow marble is: \[ \boxed{\frac{1}{2}} \]