Step-by-step explanation:
There are ₉C₂ ways to choose 2 students from 9.
There are ₁₅C₂ ways to choose 2 teachers from 15.
There are ₂₄C₄ ways to choose 4 people from 24.
Therefore, the probability is:
P = ₉C₂ ₁₅C₂ / ₂₄C₄
P = 36 × 105 / 10626
P ≈ 0.356