{ cout<< "The largest number is" <<num1 <<endl;
}
else
if (num2 > num1, num3, num4, num5, num6, num7, num8, num9, num10)
{ cout<< " The largest number" <<num2 <<endl;}
else
if (num3 > num1, num2, num4, num5, num6, num7, num8, num9, num10)
{cout<< " The largest number" <<num3 <<endl; }
else
if (num4 > num1, num2, num3, num5, num6, num7, num8, num9, num10)
cout<< " The largest number is " <<num4 <<endl;
else
if (num5 > num1, num2, num3, num4, num6, num7, num8, num9, num10)
cout<< "The largest number is " <<num5 <<endl;
else
if (num6 > num1, num2, num3, num4, num5, num7, num8, num9, num10)
cout<< "The largest number is " <<num6 <<endl;
else
if ( num7 > num1, num2, num3, num4, num5, num6, num8, num9, num10)
cout<< "The largest number is " <<num7 <<endl;
else
if ( num8 > num1, num2, num3, num4, num5, num6, num7, num9, num10)
cout<< "The largest number is " <<num8 <<endl;
else
if ( num9 > num1, num2, num3, num4, num5, num6, num7, num8, num10)
cout<< "The largest number is " <<num9 <<endl;
else
cout<< "The largest number is " <<num10 <<endl;
But that is ugly and hard to read. So a little suggestion is to store those numbers in an array and use loops(I take it that you're a beginner so I am not suggesting better algorithms).