Hello from MrBillDoesMath! 
 
Answer: 
 No
Discussion: 
 If the functions are inverses, then f(g(x)) = x for appropriate x. Consider x = 1. 
g(1) = 1/ (5(1) + 1) = 1/6
f(g(1)) = f (1/6) = 5(1/6) + 1/ (1/6) = 5/6 + 6 = 6 5/6 <> 1
Conclusion: f(g(1)) <> 1 so the functions are not inverses
 
Thank you, 
 
MrB