It shouldn't. The solution to the (300*300)/300 is 300, so either you've not copied the code across correctly or your compilers blonde (no offense :D ).
Be sure to check the code that your compiling is the same as you have provided above.
#include<iostream>
#include<conio.h>
using std::cout;
main()
{
int a=(300*300)/300;
cout<<a;
getch();
}
I write this so u can examine it. u made two mistakes. and u can use int main() if u want both will work
1 - the library is not #include<iostream.h> it's #include<iostream>
2 - if u use cout cin or a code like that u should write before main()using std::examplecode; or usingnamespace std;for all codes