D, because it is the only one that contains multiples. All others contain factors.
If you have any doubts plz let me know.
Answer:
a) 1/27
b) 16
c) 1/8
Step-by-step explanation:
a) 
One of the properties of the exponents tells us that when we have a negative exponent we can express it in terms of its positive exponent by turning it into the denominator (and changing its sign), so we would have:

And now, solving for x = 9 we have:

b) 
This is already a positive rational exponent so we are just going to substitute the value of y = 8 into the expression

c) 
Using the same property we used in a) we have:

And now, solving for z = 16 we have:

Answer:
14 months
Step-by-step explanation:
60x+60=50x+200
10x+60=200
10x=140
x=14
60(14)+60=900
50(14)+200=900
Question 4 is C and im not sure about the other questions