Bonjour

a. x + 2 + x + 4 = x + 6 = 2 (x + 3)

b. x + 1 + x + 3 = 2x + 4 = 2 (x + 2)

c. x + 1 + x + 2 = 2x + 3

d. 5x + 10x = 15x

e. 3x * 4x = 12x

f. x + x + 1 + x + 2 = 3x + 3 = 3 (x + 1)

g. x + x + 1 + x + 2 + x + 3 + x + 4 = 5x + 10 = 5 (x + 2).