Which number sentence shows the associative property of addition? Choose all that apply.
     3x(5 + 2) = 3x(5) + 3x(2)
 8z + 9p = 9p + 8z
 8 + (2 + 3) = (8 + 2) + 3
 (6 + 5) + 9 = 6 + (5 + 9)