void main is the same as return 0 my instructor wants me to use void main instead of return 0

now the problem im having is... i need to have this display 3 colums of information and its not working correctly i think its my equation but i dont know... the easyest way to see this would be to write in real quick <takes liek 15 seconds> then run it it looks like this when its semi working

Code:

/*interest rule
rate(%) of 72 actual
1 72 this is the messed up colum
2 numbers from equation
3
4
5
6
7
8
9
down to 20
*/

Code:

/*
#include <stdio.h>
#include <math.h>
void main()
{
int i,/*is the inteest rate*/ math,/*is the amount of time befor the amount double in years accourding to the 72/r ruel r= i in my case*/ actual/* amount using a more precise calculation*/;
printf("Assignment #3 Rule of 72\n");
printf("Time it takes for prices to double due to inflation.\n\n");
printf("Interst\t Rule\n");
printf("Rate(%%)\t of 72 \t Actual\n\n");
for (i=1; i<21; i++ ){
math = 72/i;
actual = 10;
while(actual <= 2*10);
actual +=(actual)*(1+i/100);
printf("%d\t %d\t %d\n", i, math, actual);
}
}*/