Réponse:
A= 5×6x - 5×3 - 3×2x + 3×4
= 30x - 15 - 6x + 12
=24x - 3
B= 5x×3x - 5x×5 + 4×3x - 4×5
= 15x² - 25x + 12x -20
= 15x² - 13x -20
C= (x+6) (5x-4-3x+1)
= (x+6) (2x-3)
