The rule below shows how the weight in ounces of a kitten depends on its age in weeks. Multiply the age in weeks by 6 and then add 9. If W = weight in ounces and x = age in weeks, which equation expresses the rule above?
A. W(x) = 9(x + 6)
B. W(x) = 6(x + 9)
C. W(x) = 6x + 9
D. W(x) = 9x + 6