Which set of expressions below does not represent equivalent expressions?

a. 8(3x + 7) and 8(3x) + 8(7)

b. 3(8x + 7) and 11x + 10

c. 7(3x + 8) and 7 · 3x + 7· 8

d. 3(7x + 8) and 21x + 24