Bonjour,
(1/7 - 1/4) × (5/2 + 5/6) = (4/28 - 7/28) × (15/6 +5/6)
= (-3/28) × (20/6)
= (-3 × 20) / (28 × 6)
= (-3 × 4 × 5) / (4 × 7 × 2 × 3)
simplification par 3 et par 4
= (-5) / (7 × 2)
= -5/14
