Answer :

Do while Loop :

#include<stdio.h>
int main()
{
int num=50;
do
{
printf("%d\n",num);
num--;
}
while (num>=40);
}

While Loop :
#include<stdio.h>
int main ()
{
int num=50;
while (num>=40)
{
printf("%d\n",num);
num--;
}
}

For Loop :

#include<stdio.h>
int main ()
{
int num;
for(num=50;num>=40;num--)
{
printf("%d\n",num);
}
}



Output :