You can mix text and variables in one statement: cout << "Score: " << score << ", Lives: " << lives << endl;. Each << adds to the output. Strings in double quotes print as literal text.
Variables print their current value. You chain them together to build complete output messages. Example: int x = 10, y = 20; cout << x << " + " << y << " = " << (x + y) << endl; prints "10 + 20 = 30".
Parentheses ensure addition happens first.