Final answer:
The probability of picking a counter from the bag that is not yellow is 7/12.
Step-by-step explanation:
The student has asked to find the probability of picking a counter from the bag which is not yellow. Since there are 48 counters in total and 20 of them are yellow, there are 48 - 20 = 28 counters that are not yellow.
The probability of picking a counter that is not yellow is therefore the number of counters that are not yellow (28) divided by the total number of counters (48).
To calculate this, we use the formula for probability P(E) = Number of favorable outcomes / Total number of possible outcomes, which gives us P(Not Yellow) = 28/48. This simplifies to P(Not Yellow) = 7/12 when reduced to its simplest form.
Therefore, the probability that a counter picked at random from the bag is not yellow is 7/12.