The given program does not execute successfully because following errors are occurred during the execution:
#include<iostream.h>
          //required for cin and cout
#include<stdio.h>
voidmain()
{
int x, sum=0,n;
           //n should be declared before use
cin>>n;
            /*Here should be input operator  >>  in place of output operator<<*/
for( X=1;X<100; X+=2)
            /*Here should be(;) in place of(,) and x in place of x. */
if (X%2==0)
sum+=X;
          /* if expression should closed in brackets() and here, should be X in place of x*/
cout<<"sum="<<sum;
/*Here should be output operator << in place of input operator >>*/
}

#include<iostream.h>
const int Multiple =3;                                                    //Correction 1
void main()
{
int value = 15;                                                             //Correction 2
for( int Counter=1; Counter<=5; Counter++, value-=2)     //Correction 3
if(value%Multiple==0)
{                                                                                
       cout<<Value*Multiple;     
       cout<<endl;
}                                                                               //correction 4                                   else 
       cout<<Value+Multiple<<endl;
}
Correction 1 Multiple must be assigned a value.
Correction 2 Variable value must be declared with datatype.
Correction 3 =< Must be replace with <=.
Correction 4 Misplace else; so after if, compound statement must be enclosed with { }.

#include<iostream.h>
#include<conio.h>
void main()
{
    int i=0;
    do
    {
          i++;
          cout<<"before the continue\n";
          continue;
           cout<<"after  the continue, should";
           cout<<"never print\n";
} while(i<3)
 cout<<"after the do loop\n";
getch();
}
Output
before the continue
before the continue
before the continue
after the do loop

#include<iostream.h>
#include<conio.h>
void main()
{
     int num;
     clrscr();
     cout<<" enter the number";
     cin>>num;
     if(num%2==0)
{
    if(num%3==0)
         cout<<"Number is divisible by 6';
else
         cout<<"Number is not divisible by 6';
}
else
         cout<<" The number is not divisible by 2 so, it is not divisible by 6";
getch();
}
Output
Enter the number 30
Number is divisible by 6 

1*1=1
1*3=3
1*5=5
2*1=2
2*3=6
2*5=10
a=32
Now k=2, b=2, c=2.666667

#include<iostream.h>
#include<conio.h>
void main()
{
     int a;
     do
     {
          cout<<"Enter a";
         cin>>a;
     }
while((a<1)||(a<6));
for(int i=0;i<=a;i++)
{
   for(int k=1;k<=(a-i);k++)
       cout<<"  "<<"  ";
   for(int j=1;j<=(2*i-1);j++)
      cout<<j<<" "<<" ";
     cout<<"\n";
}
 getch();
}