Task: Calculate a math problem with an independent variable entered by the user, in c++;

The problem I'm having is how to use the variable part, so if the equation was (2^K)/(20*K), what is the best way to set up :

So far Im on the lines of;

Obviously the equation isn't correct, just a simplified example.***Code:

#include <stdio.h>

#include <math.h>

int main

{

double math, PI, x, K;

printf("Enter a vlaue for variable K: ");

PI = (2^K)/(20*k)

................

Thanks.