def tri(t):
    # Trier chaque sous-liste individuellement
    for tab in t:
        tab.sort()
    
    for i in range(len(t)):
        for j in range(i + 1, len(t)):
            if t[i][0] > t[j][0]:
                t[i], t[j] = t[j], t[i]
    
    print(t)

tri([[3, 9, 6], [9, 3, 8], [10, 67, 55]])