g(x) : y = 1/ (x+1)
To find g-1(x), just swap y and x, then solve for y again:
x = 1/(y+1)
y+1 = 1/x
y = 1/x - 1
Make sure to double check your arithmetic, knowing that composite functions of inverses always = x.
Check (g ¤ g-1)(x)= 1/((1/x)-1) + 1) = 1/(1/x) = x
Check Again (g-1 ¤ g)(x) = 1/(1/(x+1))-1 = x+1-1 = x