Réponse:
K = (4/5 + 7/10) ÷ (5/6 - 5/8)
= (4×2/5×2 + 7/10) ÷ (5×4/6×4 - 5×3/8×3)
= (8/10+7/10) ÷ (20/24 - 15/24)
= ((8+7)/10) ÷ ((20-15)/24)
= 15/20 ÷ 5/24
= 3/4 ÷ 5/24
= 3/4 × 1/5/24
= 3/4 × 24/5
= 3×24/4×5
= 72/20
= 36/10
= 18/5.
L = 6/5 + 21/5 ÷ 14/15
(priorité à la multiplication)
= 6/5 + 21/5 ×1/14/15
= 6/5 + 21/5 × 15/14
= 6/5 + 21×15/5×14
= 6/5 + 7×3×5×3/5×1×7×2
(On simplifie 7 et 5.)
= 6/5 + 3×3/2
= 6/5 + 9/2
= 12/10 + 45/10
= 12+45/10
= 57/10.
