Can anyone help? i suck at math lol

Acertain population of bacteria demonstrates exponential growth doubles in size every 4 days. how long will it take the population to triple in size?

If f(x) = 4x – 3 and g(x) = 8x + 2, find each function value a. f[g(3)] b. g[f(5)] c. g{f[g(-4)]}

Find the value of x for which line a is parallel to line b