Bonjour,
7)
A = a - b x (c - d)
B = a - (b x c + d)
C = a x (b - (c + d))
D = 2 x b x (a - c)
E = a : (b + c)
F = (a + b) : (c x d)
8)
A = 4x + 7
A = 4 * 1 + 7
A = 4 + 7
A = 11
B = 3 + 4x - 6
B = 3 + 4 * 1 - 6
B = 3 + 4 - 6
B = 1
C = 2 (3x - 5)
C = 2 (3 * 1 - 5)
C = 2 (3 - 5)
C = 2 * - 2
C = - 4
D = 5x² + 8x - 6
D = 5 * 1² + 8 * 1 - 6
D = 5 + 8 - 6
D = 7.