\( 10 \quad 0.5 \) points If three coins are tossed at the same time, use a tree diagram to find the probability that at least two of the coins will land tails up. State your answer as a fraction. type your answer..

Step 1 ：1. Enumerate possible outcomes of 3 coin tosses: {TTT, TTH, THT, THH, HTT, HTH, HHT, HHH}

Step 2 ：2. Count outcomes with at least 2 tails: {TTT, TTH, THT, HTT}

Step 3 ：3. Calculate probability: \( \frac{\text{Outcomes with 2 or more tails}}{\text{Total outcomes}} = \frac{4}{8} = \frac{3}{8} \)