How do you tell which radical is the largest? (elementary algebra)

What is the y intercept of f(x)=(1/2)^x?

How do you use the elimination method for this question? explain, because i really want to understand!

An initial investment of $100 is now valued at $150. the annual interest rate is 5%, compounded continuously. the equation 100e0.05t = 150 represents the situation, where t is the number of years the money has been invested. about how long has the money been invested? use your calculator and round to the nearest whole number. years