Actually Welcome to the Concept of the Inverse of real function.
Let's consider here, g(n) = y ,
so we get as,
![y = \sqrt[3]{ \frac{n - 1}{2} }](https://tex.z-dn.net/?f=y%20%3D%20%20%5Csqrt%5B3%5D%7B%20%5Cfrac%7Bn%20-%201%7D%7B2%7D%20%7D%20)
no, cubing the power both side we get as,
=>
now,
so finally, we get as,
=>
hence,here, n = inverse of the g(n) function.
so,
g^-1 (n) = 2y^3+1.
5*10^3 * 5*10^7= 5*5 *10^3*10^7=25*10^10
Generally u are allowed to leave it as it is but if no
25*10^10=25 * 10000000000 = 250000000000
Here u are!
I got 4x if that isn’t right I will check again
So firstly, subtract x on both sides: 
Next, divide -2 on both sides, and your answer will be y = 1/2x - 3/2 , or the last option.
