Suppose it took x years for an investment to grow from $100 to $200 at a fixed

Question:

Suppose it took x years for an investment to grow from $100 to $200 at a fixed compound rate of return. How many more years will it take to earn an additional
a. $100?
b. $200?
c. $300? In each case, pick an answer from:
(i) More than x years,
(ii) Less than x years,
(iii) Exactly x years.