If f(x)=3xf(x) = 3xf(x)=3x and g(x)=x+2g(x) = x + 2g(x)=x+2, which of the following is (g∘f)(x)(g \circ f)(x)(g∘f)(x)?
3x+23x + 23x+2
3x+63x + 63x+6
3(x+2)3(x + 2)3(x+2)
x+5x + 5x+5