Ответ:
20 × 9 × 5 = 20 × 5 × 9 = 100 × 9 = 900.
15 × 7 × 4 = 15 × 4 × 7 = 60 × 7 = 420.
16 × 4 × 5 = 16 × (4 × 5) = 16 × 20 = 320.
20 × 9 × 5 = 20 × 5 × 9 = 100 × 9 = 900.
15 × 7 × 4 = 15 × 4 × 7 = 60 × 7 = 420.
16 × 4 × 5 = 16 × (4 × 5) = 16 × 20 = 320.