The code doesn't give me correct decimal answers

Question

The code doesn't give me the right decimal answers after calculating, and it also doesn't prompt the user to re enter the right value when it's less than 9,as I expected. I'm new in programming, can I please get help on what to do. Here is the code

#include <cs50.h>
#include <stdio.h>

int main(void)
{
    float i = get_float("first population: ");
    float j = get_float("second population: ")

    if (i < 9)
    {
        printf ("%f",'i');
    }
    if (j < 9)
    {
        printf ("%f",'j');
    }
    float n = (i/3);
    float m = (i/4);

    float d = (n - m);
    float a = (i + d);

    float x = (j - i);
    float y = (j/a);

    printf ("%f", y\n);
}

Answer 1

The problem is that you have no logic to retry if the input is not what you want.

if you want the user to be reprompted for another input if i < 9 for example you would have to do the following:

float i = 0;
while ( i < 9 ) {
    i = get_float("first population: ");
}

That will insure that they have entered a value that is at least 9. However I dont think you want a float there. Assuming you are doing the first problem about population you can't have a half a llama. So 10.5 wouldnt be valid.. I think what you want is an integer.

Note I'm also going to rename variables to give them some meaning

int start = 0;  # note change to int
while ( start < 9 ) 
{   // using a while loop says while start is less than 9 do the actions inside here
    // note I have used get_int and changed prompt to match the instructions
    start = get_int("Start size: ");
}

The second value should also be an integer and is end value

int end = 0;
while ( end < start )
{
    end = get_int("End size: ");
}

now we have valid start and end population targets.

then we do the next phase

int current = start;
//???? need something here to make this cycle repeat until you reach the goal
int born = current / 3;
int dead = current / 4;
int current = current + born - dead;
// ???? and need something here to count the number of years it takes

You cant just do this once and divide by difference by what amounted to (start + born - dead) because a different amount will be born and die each year, you have to iteratively do this out in a loop of some kind. I leave it up to you to figure that part out but I have left some hints in place.