Mẫu: 4 × 12 + 4 × 16 – 4 × 8 = 4× (12 + 16 – 8)
= 4 ×20 = 80
3 ×17 + 3 ×25 - 3×2 = …………………
= …………………
3 × 17 + 3 × 25 – 3 × 2
= 3 × (17 + 25 – 2)
= 3 × 40
= 120
-- Mod Toán lớp 4