(a)
In order to graph y = 2f(x), we just need to use the values of y two times higher than the values of y = f(x), that is, a vertical stretch. So we have:
(In black: y = 2f(x), in red: y = f(x))
(b)
In order to graph y = g(2x), we just need to use half the values of x from y = g(x), that is, a horizontal compression. So we have:
(in green: y = g(2x), in blue: y = g(x))
