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Réponse :

Bonjour

Explications étape par étape

A1 = 7 * x = 7x

A2 = (B + b) * h/2

A2 = (8 + x) * 4/2

A2 = 16 + 2x

A1 = A2

7x = 16 + 2x

7x - 2x = 16

5x = 16

x = 16/5

x = 3,2