f(x) = ex and g(x) = ln x
E is a special number where e^x differentiates to e^x. Ln (x) is Log base e of x.
Given that log base 10 of 10 is 1, and log base n of n is 1, ln(e) is also 1. So fg(x) = e^(g(x)) = e^(log x) = x. GF(x) = ln(f(x)) = ln(e^x)= x * ln(e) (using log laws, bringing power to the front), = x*1 = x.
Therefore fg(x) = x = gf(x)
Please let me know if this answer is any good or needs further explination.