Bonjour,
soit p, le pourcentage de réduction (p%)
70 * (1 - p/100) = 50
70 * (100/100 - p/100) = 50
70 * ((100 - p)/100) = 50
(70 * 100 + 70 * (-p))/100 = 50
7 000 - 70p = 50 * 100
7 000 - 70p = 5 000
7 000 - 5 000 = 70p
2 000 = 70p
2 000 / 70 = p
p ≈ 28,57%