Bonjour,
3x + 21 = 3 × x + 3 × 7 = 3 × (x + 7)
9x - 36 = 9 × x - 9 × 4 = 9 × (x - 4)
60 - 12y = 12 × 5 - 12 × y = 12 × (5 - y)
15 - 3x = 3 × 5 - 3 × x = 3 × (5 - x)
6x + 9 = 3 × 2x + 3 × 3 = 3 × (2x + 3)
27x² - 24 = 3 × 9x² - 3 × 8 = 3 × (9x² - 8)
12 - 39x = 3 × 4 - 3 × 13x = 3 × (4 - 13x)
