Which two expressions are equivalent?​​​​​​​

a. 7(3 + x) and 7• 3 + 3 • x

b. 7 + 3 + x and (7 + 3) + x

c. 7 • x • 3 and 7(x + 3)

d. 7 ÷ (3 – x) and 7 ÷ (x – 3)