Answer:
[tex]\frac{7x}{1+3x}[/tex]
Step-by-step explanation:
If [tex]f(x)=\frac{7}{x+3}[/tex] and [tex]g(x)=\frac{1}{x}[/tex]
Then:
[tex](fog)(x) = f(g(x))=\frac{7}{g(x)+3} =\frac{7}{\frac{1}{x}+3 } =\frac{7}{\frac{1}{x}+\frac{3x}{x} }=\\ = \frac{7}{\frac{1+3x}{x} }=\frac{7x}{1+3x}[/tex]