solution

#include<iostream.h>
#include<conio.h>

int main()
{
 int angle1,angle2,angle3;
 cout<<"Enter the three angles of triangle:";
 cin>>angle1>>angle2>>angle3;

 if (angle1+angle2+angle3==180)
  cout<<"Triangle is valid";
 else
  cout<<"Triangle is not valid";

 getch();
 return 0;
}