I am having difficulty solving:  The function f(x) = 300(0.5) x/60 models the amount in pounds of a particular radioactive material stored in...

I am having difficulty solving:  The function f(x) = 300(0.5) ^x/60 models the amount in pounds of a particular radioactive material stored in a concrete vault, where x is the number of years since the material was put into the vault. Find the amount of radioactive material in the vault after 170 years.